key: cord-0835657-salm69jn authors: Youssef, Fadia S.; Alshammari, Elham; Ashour, Mohamed L. title: Bioactive Alkaloids from Genus Aspergillus: Mechanistic Interpretation of Their Antimicrobial and Potential SARS-CoV-2 Inhibitory Activity Using Molecular Modelling date: 2021-02-13 journal: Int J Mol Sci DOI: 10.3390/ijms22041866 sha: ab051b1ddb5b54ca65f65d46c6babe356da7e60d doc_id: 835657 cord_uid: salm69jn Genus Aspergillus represents a widely spread genus of fungi that is highly popular for possessing potent medicinal potential comprising mainly antimicrobial, cytotoxic and antioxidant properties. They are highly attributed to its richness by alkaloids, terpenes, steroids and polyketons. This review aimed to comprehensively explore the diverse alkaloids isolated and identified from different species of genus Aspergillus that were found to be associated with different marine organisms regarding their chemistry and biology. Around 174 alkaloid metabolites were reported, 66 of which showed important biological activities with respect to the tested biological activities mainly comprising antiviral, antibacterial, antifungal, cytotoxic, antioxidant and antifouling activities. Besides, in silico studies on different microbial proteins comprising DNA-gyrase, topoisomerase IV, dihydrofolate reductase, transcriptional regulator TcaR (protein), and aminoglycoside nucleotidyl transferase were done for sixteen alkaloids that showed anti-infective potential for better mechanistic interpretation of their probable mode of action. The inhibitory potential of compounds vs. Angiotensin-Converting Enzyme 2 (ACE2) as an important therapeutic target combating COVID-19 infection and its complication was also examined using molecular docking. Fumigatoside E showed the best fitting within the active sites of all the examined proteins. Thus, Aspergillus species isolated from marine organisms could afford bioactive entities combating infectious diseases. Recently, marine-derived fungi have gained significant attention as promising therapeutic approaches for the treatment of a wide array of human ailments and as successful tools for drug discovery [1] . This is mainly attributed to their richness by a diverse array of secondary metabolites comprising terpenoids, alkaloids, peptides, lactones and steroids. These promising activities are represented by antiviral, antibacterial, anti-inflammatory and anticancer activity [2] . The significant diversity in physical and chemical structure of the environment where the marine-derived fungi grow has greatly reflected by the vast structural and functional variation in their produced secondary metabolites and their biological activities [3] . Meanwhile, marine-derived fungal metabolites displayed a promising physico-chemical behavior and oral-bioavailability, constituting a safer therapeutic alternative when compared to synthetic molecules that are considerably important in the process of pharmaceutical dosage form formulation [4, 5] . Moreover, many alkaloids were previously isolated from marine fungi and showed a vast array of biological activities [6] [7] [8] [9] . Genus Aspegillus represents a widely spread genus of fungi that are highly popular of possessing a potent medicinal potential comprising mainly antimicrobial, cytotoxic and Moreover, many alkaloids were previously isolated from marine fungi and showed a vast array of biological activities [6] [7] [8] [9] . Genus Aspegillus represents a widely spread genus of fungi that are highly popular of possessing a potent medicinal potential comprising mainly antimicrobial, cytotoxic and antioxidant activities that are highly attributed to its richness by alkaloids, terpenes, steroid and polyketons. These secondary metabolites reflect the considerable importance of genus Aspergillus both in the scientific and pharmaceutical industries levels [10] . Thus, this review aimed to comprehensively explore the diverse alkaloids isolated and identified from different species of genus Aspergillus that were found to be associated with different marine organisms regarding their chemistry and biology. Classification was done on the basis of alphabetical arrangement of species. Around 174 alkaloid metabolites were reported, 66 of which showed important biological activities mainly comprising antiviral, antibacterial, antifungal, cytotoxic, antioxidant and antifouling activities. In addition, data illustrating the bioactive alkaloids obtained from previously mentioned fungal strains, their sources and biological properties are compiled in Table 1 for better representation of the collected data. A pie chart illustrating the different biological activities for the bioactive alkaloids of genus Aspergillus was also provided. Besides, in silico studies on different microbial proteins were done for sixteen alkaloids that showed anti-infective potential for better mechanistic interpretation of their probable mode of action. In addition, the inhibitory potential of these compounds vs. Angiotensin-Converting Enzyme 2 (ACE2) as an important therapeutic target combating COVID-19 infection and its complication was also examined using molecular docking to it can act as a guide for researchers who wish to continue exploring the anti-infectious potential of alkaloid derived from genus Aspergillus. Aspergillus species are highly popular due to the presence of a wide variety of alkaloids belonging to diverse classes. Prenylated indole and quinazolinone alkaloids were isolated from A. carneus, a marine associated Aspergillus species, while the former is represented by carneamides A-C (1-3); however, the latter is represented by carnequinazolines A-C (4) (5) (6) . Unfortunately, none of the isolated compounds revealed any antimicrobial or cytotoxic activities ( Figure 1 ) [11] . In depth phytochemical investigation of A. flavus resulted in the isolation of two alkaloids of diketopiperazine class; namely, ditryptophenaline (7) and 3[(1H-indol-3-yl) methyl]-6-benzylpiperazine-2,5-dione (8) . Their structures were unambiguously elucidated via accurate analysis of their spectroscopic data ( Figure 1 ) [12] . Regarding A. fumigatus, it revealed the presence of plethora of alkaloids (Figures 2 and 3 ) which are represented by fumitremorgin C (9), fumiquinazoline C (10), verruculogen (11) , spirotryprostatin F (12), spirotryprostatin A (13), 12,13-dihydroxyfumitremorgin C (14) , tryptoquivaline F (15), 6-bisdethiobis(methylthio)gliotoxin (16), 6-methoxyspirotryprostatin B (17) . Compounds (9) (10) (11) (12) (13) effectively stimulate the growth of buckwheat seedlings at very low concentration estimated by 10-16 µM [13] , however compounds (16) (17) potentiate the growth of seedling roots of Zea mays in an effective manner [14] . Besides, fumiquinazoline A (18), fumiquinazoline C (10), fumiquinazoline F (19) , fumiquinazoline G (20) , pseurotin A (21), as well as tryptoquivaline J (22) , were isolated from the same Aspergillus species. All the isolated six alkaloid metabolites showed a substantial inhibitory activity on tsFT210 cells proliferation; however, fumiquinazoline C and pseurotin A effectively inhibited BEL-7402, A-549, P388 and HL60 proliferation [15] . Furthermore, costaclavine (23) , fumgaclavine A (24) and C (25) , which were isolated from A. fumigatus together with two new alkaloids of indole type 2-(3,3-dimethylprop-1-ene)-costaclavine (26) and 2-(3,3-dimethylprop-1-ene)epicostaclavine (27) revealed mild cytotoxic effect vs. P388, mouse leukemia cancer cells [16] . Meanwhile, new alkaloids isolated from A. fumigatus displayed a potent antimicrobial activity in which fumigatoside E (28) showed antifungal activity vs. Fusarium oxysporum with MIC equals 1.56 µg/mL. Besides, fumigatoside F (29) showed a considerable activity against A. baumanii with MIC equals 6.25 µg/ mL. In addition, fumiquinazoline C (10), fumiquinazoline G (20) and epi-aszonalenin A (30) showed moderate potential against A. baumanii, two S. aureus strains, K. pneumonia, Fusarium oxysporum cucumerinu and momordicae with MIC ranging from 1.5 to 25 µg/mL, in which streptomycin was used as a positive antibacterial standard drug and nystatin as a positive antifungal standard drug. Meanwhile, fumiquinazoline G showed the greatest activity with MICs equal to 1.56 and 0.78 µg/mL, against the Staphylococcus aureus strains [17] . Moreover, another study carried on A. fumigatus revealed that some of its alkaloids showed a notable in-vitro antiproliferative effect such as pseurotin A (41), 14-norpseurotin A (31), pseurotin A1 (32), FD-838 (33) however other alkaloids as 14-hydroxyterezine D (34), demethoxyfumitremorgin C (35) and terezine D (36) were also isolated [18] . Furthermore, four new alkaloids of quinazolinone type which are aniquinazolines A-D (37-40) were isolated from A. nidulans, which was associated with the leaves of Rhizophora stylosa, marine plant. Compounds (37-40) revealed a significant lethal effect on brine shrimp displaying LD50 of 1.27, 2.11, 4.95 and 3.42 µM, in a respective manner which is superior to the positive control colchicine. However, none of these compounds exhibited any antibacterial activity vs. Escherichia coli and S. aureus or any cytotoxic effect on HL-60, BEL-7402, K562 and MDA-MB-231 cancer cells ( Figure 4 ) [19] . A. ochraceus is also a rich source of alkaloids of benzodiazepine type such as 2hydroxycircumdatin C (41) and 2,3-dihydro-7-methoxy-1Hpyrrolo[2,1-c] [1, 4] benzodiazepine -5,11(10H,11aH)-dione (42) that are considered to be new naturally occurring alkaloids in addition to known compounds as circumdatin C (43), circumdatin D (44), circumdatin F (45), selerotiamide (46) and notoamide B (47). 2-Hydroxycircumdatin C showed a potent antioxidant power as evidenced by its IC50 that is estimated by 9.9 µM in DPPH radical scavenging assay showing a superior activity comparable to butylated hydroxytoluene, a familiar synthetic positive control with IC 50 = 88.2 µM. However, circumdatin C and D displayed mild antioxidant activity with IC 50 value more than 100 µM in the same assay. None of compounds (41) (42) (43) (44) (45) (46) (47) revealed any antibacterial potential against S. aureus or E. coli or antifungal effect vs. A. niger [20] . Concerning A. ostianus, two heptacyclic alkaloidal compounds of stephacidin class were isolated from its culture medium namely notoamide F (48) and 21-hydroxystephacidin (49) (Figure 4 ) [21] . Furthermore, four new alkaloids of quinazolinone type which are aniquinazolines A-D (37) (38) (39) (40) were isolated from A. nidulans, which was associated with the leaves of Rhizophora stylosa, marine plant. Compounds (37-40) revealed a significant lethal effect on brine shrimp displaying LD50 of 1.27, 2.11, 4.95 and 3.42 μΜ, in a respective manner which is superior to the positive control colchicine. However, none of these compounds exhibited any antibacterial activity vs. Escherichia coli and S. aureus or any cytotoxic effect on HL-60, BEL-7402, K562 and MDA-MB-231 cancer cells ( Figure 4 ) [19] . Meanwhile, a series of oxindole alkaloids represented by speradines C-H (50-55) were isolated from A. oryzae, which showed a mild cytotoxic effect on HeLa cell line ( Figure 4 ) [22, 23] . Furthermore, A. puniceus is a good source of new alkaloids from which eight new diketopiperazine-type alkaloids were isolated from the extract of its culture broth. Four of these new diketopiperazine alkaloids contain oxepin moiety however the other four contain quinazolinone moiety. The formers are represented by oxepinamides H-K (56-59); meanwhile, the latters were represented by puniceloids A-D (60-63) (Figure 4 ). Noteworthy to highlight that all the new eight isolated compounds revealed a potent transcriptional stimulation of liver X receptor α displaying EC 50 ranging between 1.7 and 50 µM with puniceloids C and D showed the highest agonist behavior [24] . A. sydowii in which 6-methoxyspirotryprostatin B showed mild cytotoxic activity against HL-60 cells displaying IC50 of 9.71 μM [28] . A. tamari, a marine derived fungal strain, also yielded a new alkaloid possessing oxindole pentacylcic skeleton termed speradine A (78) [29] meanwhile A. terreus culture extract afforded a new alkaloid which is terremide C (79) ( Figure 5 ) [30] . A. versicolor is highly popular by the presence of a large number of alkaloids ( Figure 6 ), which are represented by asperversiamides A-H (80-87), which are indole alkaloids characterized by the presence of a linear fused prenyl groups and cottoquinazoline A (88) [7, 31] . Asperversiamide G (86) displayed a significant anti-inflammatory potential evidenced by the pronounced inhibition of iNOS with IC50 value of 5.39 μM [7] . Additionally, ten new alkaloids of diketopiperazine class were isolated from A. versicolor, pyranamides A-D (89-92), secopyranamide C (93), protuboxepin F-J (94-98) in addition to previously isolated compounds which were protuboxepin C (99) and protuboxepin E (100). Protuboxepin G and E displayed mild cytotoxic activity vs. 786-O, OS-RC-2 and ACHN [9] . Further investigation of the coral derived fungus, A. versicolor, resulted in the exploration of six new alkaloids in the polycyclic form, which are versiquinazolines L-Q (101-106). Versiquinazolines P and Q displayed potent prohibition of thioredoxin reductase (TrxR) revealing IC50 of 13.6 and 12.2 μM, respectively being superior in activity relative to curcumin, the positive control, with IC50 of 25 μM accompanied by weak cytotoxic effect. This consequently, provides an evidence on the potential use of both A. sydowii was subjected to an intense phytochemical investigation that led to the isolation of many indole alkaloids, fumiquinazoline D and E (69-70) and cyclotryprostatin B (71) in addition to 12,13-dihydroxyfumitremorgin C (14) , fumiquinazoline A (18), fumiquinazoline F (19) and fumiquinazoline G (20) ( Figure 5 ). These compounds were tested for their antifouling activity via assessing their inhibitory effect on the settlement of B. neritina larvae, at a concentration of 25 µg/mL, fumiquinazoline D, fumiquinazoline G and cyclotryprostatins B showed significant antifouling activity [8] . Besides, fumiquinazoline B (72), fumiquinazoline C (10), fumitremorgin B (73), cyclotryprostatin E (74) and [4-(2-methoxyphenyl)-1-piperazinyl][(1methyl-1H-indol-3-yl)]methanone (75) were also isolated from A. sydowii. Compound (10) revealed cytotoxic activity against P388, HL60, A549, FT210 and BEL-7402 with IC 50 ranging between 1 × 10 −5 and 1 × 10 −4 mol/L-1 [26, 27] . Additionally, 18-oxotryprostatin A (96), 6-methoxyspirotryprostatin B (17) and 14-hydroxyterezine D (77) were also isolated from A. sydowii in which 6methoxyspirotryprostatin B showed mild cytotoxic activity against HL-60 cells displaying IC 50 of 9.71 µM [28] . A. tamari, a marine derived fungal strain, also yielded a new alkaloid possessing oxindole pentacylcic skeleton termed speradine A (78) [29] meanwhile A. terreus culture extract afforded a new alkaloid which is terremide C (79) ( Figure 5 ) [30] . A. versicolor is highly popular by the presence of a large number of alkaloids ( Figure 6 ), which are represented by asperversiamides A-H (80-87), which are indole alkaloids characterized by the presence of a linear fused prenyl groups and cottoquinazoline A (88) [7, 31] . Asperversiamide G (86) displayed a significant anti-inflammatory potential evidenced by the pronounced inhibition of iNOS with IC 50 value of 5.39 µM [7] . Additionally, ten new alkaloids of diketopiperazine class were isolated from A. versicolor, pyranamides A-D (89-92), secopyranamide C (93), protuboxepin F-J (94-98) in addition to previously isolated compounds which were protuboxepin C (99) and protuboxepin E (100). Protuboxepin G and E displayed mild cytotoxic activity vs. 786-O, OS-RC-2 and ACHN [9] . Further investigation of the coral derived fungus, A. versicolor, resulted in the exploration of six new alkaloids in the polycyclic form, which are versiquinazolines L-Q (101-106). Versiquinazolines P and Q displayed potent prohibition of thioredoxin reductase (TrxR) revealing IC 50 of 13.6 and 12.2 µM, respectively being superior in activity relative to curcumin, the positive control, with IC 50 of 25 µM accompanied by weak cytotoxic effect. This consequently, provides an evidence on the potential use of both compounds in the control of microenvironment of tumor progression and metastasis [32] . In addition, versicoloid A and B (107-108), 3,6-O-dimethylviridicatin (109) and 3-O-methylviridicatol (110) were also isolated from A. versicolor, in which versicoloid A and B displayed a potent anti-fungal activity with MIC of 1.6 µg/mL against Colletotrichum acutatum approaching cycloheximide, the positive control drug, that showed MIC of 6.4 µg/mL. [33] . Concerning A. westerdijkiae, circumdatins K and L (111, 112), two new alkaloids of benzodiazepine type, 5-chlorosclerotiamide (113) and 10-epi-sclerotiamide (114), which are two new indole alkaloids carrying a prenyl moiety in addition to known alkaloid compounds which are circumdatin G (115), sclerotiamide (116), notoamide C (117), notoamide I (118) and circumdatin F (45) (Figure 7) . However, none of the A. westerdijkiae isolated compounds showed cytotoxic effect vs. MCF-7, HL-60, A549 or K562 displaying IC 50 greater than 10 µM. However, sclerotiamide showed a lethal effect on brine shrimps computed by 68% at 5 µg/mL [34] . compounds in the control of microenvironment of tumor progression and metastasis [32] . In addition, versicoloid A and B (107-108), 3,6-O-dimethylviridicatin (109) and 3-O-methylviridicatol (110) were also isolated from A. versicolor, in which versicoloid A and B displayed a potent anti-fungal activity with MIC of 1.6 μg/mL against Colletotrichum acutatum approaching cycloheximide, the positive control drug, that showed MIC of 6.4 μg/mL. [33] . benzodiazepine type, 5-chlorosclerotiamide (113) and 10-epi-sclerotiamide (114), which are two new indole alkaloids carrying a prenyl moiety in addition to known alkaloid compounds which are circumdatin G (115), sclerotiamide (116), notoamide C (117), notoamide I (118) and circumdatin F (45) (Figure 7) . However, none of the A. westerdijkiae isolated compounds showed cytotoxic effect vs. MCF-7, HL-60, A549 or K562 displaying IC50 greater than 10 μM. However, sclerotiamide showed a lethal effect on brine shrimps computed by 68% at 5 μg/mL [34] . Besides, a plethora of alkaloid compounds were isolated from miscellaneous Aspergillus species such as fumiquinazoline S (119), fumiquinazolines F (29) and L (120), isochaetominines A-C (121-123), 14-epi-isochaetominine C (124) (Figure 8 ). All these compounds revealed a mild inhibitory effect on Na(+)/K(+)-ATPase [35] . Additionally, asperginine (125), an alkaloid with a rare skeleton, and misszrtine A (126), an indole alkaloid with novel skeleton, possess phenylpropanoic amide arm attached to N-isopentenyl tryptophan methyl ester were isolated from two different Aspergillus species. The cytotoxic activity of the former was evaluated using MTT assay against human HCT116 and PC3 (prostate cancer cells) but it revealed no activity against the previously mentioned cell lines [36] . However the latter was assessed for its cytotoxic activity on HL60 and LNCaP and revealed a promising activity with IC50 value of 3.1 and 4.9 μM, respectively owing to the presence of indole nitrogen [37] . Besides, asperindoles A-D (127-130), new jndole alkaloids possessing diterpene structure, were also isolated from Aspergillus species. Asperindoles C and D possess a 2-hydroxyisobutyric acid moiety; however, asperindole A revealed a potent cytotoxic activity on both hormone therapy-resistant and sensitive PC-3 (Human prostate cancer cells) in addition to 22Rv1 cancer cells (human prostate carcinoma epithelial cell line) at low concentrations calculated in micromolar [38] . Golmaenone (131), new alkaloid with diketopiperazine skeleton, and neoechinulin A (132) were also isolated from Aspergillus species (Figure 8 ). Both compounds revealed a potent antioxidant activity evidenced by their IC50 values which are 20 and 24 μM, respectively in 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity assay comparable to that of ascorbic acid (IC50 = 20 μM). Their Besides, a plethora of alkaloid compounds were isolated from miscellaneous Aspergillus species such as fumiquinazoline S (119), fumiquinazolines F (29) and L (120), isochaetominines A-C (121-123), 14-epi-isochaetominine C (124) (Figure 8 ). All these compounds revealed a mild inhibitory effect on Na(+)/K(+)-ATPase [35] . Additionally, asperginine (125), an alkaloid with a rare skeleton, and misszrtine A (126), an indole alkaloid with novel skeleton, possess phenylpropanoic amide arm attached to N-isopentenyl tryptophan methyl ester were isolated from two different Aspergillus species. The cytotoxic activity of the former was evaluated using MTT assay against human HCT116 and PC3 (prostate cancer cells) but it revealed no activity against the previously mentioned cell lines [36] . However the latter was assessed for its cytotoxic activity on HL60 and LNCaP and revealed a promising activity with IC 50 value of 3.1 and 4.9 µM, respectively owing to the presence of indole nitrogen [37] . Besides, asperindoles A-D (127-130), new jndole alkaloids possessing diterpene structure, were also isolated from Aspergillus species. Asperindoles C and D possess a 2hydroxyisobutyric acid moiety; however, asperindole A revealed a potent cytotoxic activity on both hormone therapy-resistant and sensitive PC-3 (Human prostate cancer cells) in addition to 22Rv1 cancer cells (human prostate carcinoma epithelial cell line) at low concentrations calculated in micromolar [38] . Golmaenone (131), new alkaloid with diketopiperazine skeleton, and neoechinulin A (132) were also isolated from Aspergillus species (Figure 8) . Both compounds revealed a potent antioxidant activity evidenced by their IC 50 values which are 20 and 24 µM, respectively in 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity assay comparable to that of ascorbic acid (IC 50 = 20 µM). Their antioxidant behaviour was further consolidated by their high UV-A (320-390 nm) protecting capability with ED 50 values equal to 90 and 170 µM, respectively exceeding that of oxybenzone, the most popular consumed sunscreen (ED 50 = 350 µM) [39] . Additionally, a series of prenylated indole alkaloids, notoamide A (133), notoamide B (47), notoamide C (117), notoamide E (134), notoamide F (68), notoamides G and H (135-136), notoamide I (118), notoamide J-R (137-145) were isolated from mussel-associated Aspergillus species. Notoamides A-C revealed a notable cytotoxic effect vs. cancer cells meanwhile notoamide I revealed a weak cytotoxic effect against HeLa cells with IC 50 = 21 µg/mL. Additionally, notoamide A revealed a potent lethal effect on brine shrimps estimated by 63.0% at 5 µg/mL [40] [41] [42] . Additionally, versicolamide B and notoamides L-N were isolated from a marine derived Aspergillus species [41] . tecting capability with ED50 values equal to 90 and 170 μM, respectively exceeding that of oxybenzone, the most popular consumed sunscreen (ED50 = 350 μM) [39] . Additionally, a series of prenylated indole alkaloids, notoamide A (133), notoamide B (47), notoamide C (117), notoamide E (134), notoamide F (68), notoamides G and H (135-136), notoamide I (118), notoamide J-R (137-145) were isolated from mussel-associated Aspergillus species. Notoamides A-C revealed a notable cytotoxic effect vs. cancer cells meanwhile notoamide I revealed a weak cytotoxic effect against HeLa cells with IC50 = 21 μg/mL. Additionally, notoamide A revealed a potent lethal effect on brine shrimps estimated by 63.0% at 5 μg/mL [40] [41] [42] . Additionally, versicolamide B and notoamides L-N were isolated from a marine derived Aspergillus species [41] . showed antifungal activity [56] were also isolated from genus Aspergillus. A pie chart illustrating the different biological activities for the bioactive alkaloids of genus Aspergillus was illustrated in Figure 10 . Besides, prenylated indoles spirotryprostatins C-E and 13-oxoverruculogen and their cytotoxic effects upon a panel of cancer cell lines where spirotryprostatin E showed the most potent cytotoxic effect vs. MOLT-4, HL-60 and A-549 cells with IC50 ranging between 2.3-3.1μm [57] . Moreover, protuboxepins A and B (146-147) which possess oxepin moieties in addition to protubonines A and B, two diketopiperazine-type alkaloids (148-149) and aspergicin (150) were also isolated from Aspergillus species (Figure 9 ). Protubonines A exhibited a weak inhibition on cancer cells [43] ; however, aspergicin showed a potent antibacterial activity against Bacillus subtilis, Staphylococcus aureus and Staphylococcus epidermidis, Bacillus proteus, Bacillus dysenteriae and Escherichia coli displaying MICs ranging from 15.62 to 62.50 µg/mL [44] . Additionally, two new prenylated indole alkaloids, 17-epi-notoamides Q and M (151-152) and stephacidin A (153) were also isolated from marine-associated Aspergillus species (Figure 9 ). None of them showed any cytotoxic activity vs. human promyelocytic leukemia HL-60 cell lines meanwhile only stephacidin A revealed antimicrobial vs. Staphylococcus epidermidis with MIC equals 14.5 µM [45] . Additionally, azonazine (154), 7α,14-dihydroxy-6β-p-nitrobenzoylconfertifolin (155), 9α,14-dihydroxy-6β-p-nitrobenzoylcinnamolide (156), 5-(1H-indol-3-ylmethyl) imidazolidine-2,4-dione (157) and oxepinamide E (158) were also isolated from Aspergillus species. Compounds (155-156) displayed a potent inhibition to influenza virus strains H1N1 and H3N2, with IC 50 of 36.0 and 12.0 µM, respectively, for compound (155) and 7.4 and 4.3 µM, respectively, for the two viruses for compound (156); meanwhile, compound (154) showed no activity [46, 47] . Additionally, a new alkaloid, 3-((1-hydroxy-3-(2-methylbut-3-en-2-yl)-2-oxoindolin-3yl)methyl)-1-methyl-3,4-dihydrobenzo[e] [1, 4] diazepine-2,5-dione (159) in addition to a known one, cytochalasin Z17 (160) were isolated from certain Aspergillus species. They revealed a potent antimicrobial activity vs. a number of microbes with compound (159) exerted a selective inhibition on Vibrio harveyi, V. natriegens, V. proteolyticus, V. carchariae showing MIC values between 0.0001 and 1 µg/mL; meanwhile, compound (160) showed a significant inhibition to Roseobacter litoralis showing MIC of 0.0001 µg/mL [48] . In addition, 12,13-dihydroxy fumitremorgin C (161), fumitremorgin C (9) and bis(dethio)bis(methylthio)gliotoxin (16) were isolated from certain Aspergillus species associated with the collected sediments existing in the northeast coast of Brazil ( Figure 9 ) [49] . Additionally, new alkaloids, acremolin B (162), oximoaspergillimide (163) in addition to acremolin (164) were obtained as a result of the purification of the cultural extract of marine derived Aspergillus species; however, none of the compounds showed cytotoxic or antibacterial behavior [50, 51] . Besides, new alkaloids, SF5280-415 (165), diketopiperazine dimer, and a closely related compound (166) were obtained from a marine associated Aspergillus species. Both compounds (165-166) revealed a potent inhibitory potential to protein tyrosine phosphatase 1B in an assay done using p-nitrophenyl phosphate as a substrate with IC 50 values equal to 14.2 and 12.9 µM, for both compounds, respectively. Thus, both compounds can serve as natural candidates in the management of obesity as well as diabetes [52] . In an additional study carried on marine derived Aspergillus species, its isolated compounds bisdethiobis(methylthio)-dehydrogliotoxin (167), gliotoxin (168), 13-oxofumitremorgin B (169), fumitremorgin C (9), fumiquinazoline C (10), 12,13dihydroxy-fumitremorgin C (14), bisdethiobis-(methylthio)gliotoxin (16), fumiquinazoline A (18), fumiquinazoline F (19) , cyclotryprostatin B (71) and fumitremorgin B (73) were assessed for their anti-tuberculosis potential, cytotoxicity and antibacterial. Gliotoxin and 12,13-dihydroxy-fumitremorgin C displayed a considerable inhibition to Mycobacterium tuberculosis with MIC values less than 0.03 and 2.41 µM, respectively, In addition, gliotoxin exhibited potent cytotoxic activity vs. the three cell lines, A549, K562 and Huh-7 cell lines as evidenced by their IC 50 values which are 0.015, 0.191 and 95.4 µM, respectively. Gliotoxin also revealed antibacterial potential vs. Staphylococcus aureus, Escherichia coli and Salmonella showing no antiviral or COX-2 inhibitory activity [53] . In another study performed on the marine gorgonian Aspergillus, aspergillspins A-B, new alkaloids with βcarboline moiety (170, 171) and aspergillspins C-E (172-174), new alkaloids with quinolone structure were isolated and their antibacterial and cytotoxic activity were evaluated [54] . Besides, the hydroxypyrrolidine alkaloid preussin showed notable antibacterial activity [55] and diketopiperazine alkaloid mactanamide showed antifungal activity [56] were also isolated from genus Aspergillus. A pie chart illustrating the different biological activities for the bioactive alkaloids of genus Aspergillus was illustrated in Figure 10 . Besides, prenylated indoles spirotryprostatins C-E and 13-oxoverruculogen and their cytotoxic effects upon a panel of cancer cell lines where spirotryprostatin E showed the most potent cytotoxic effect vs. MOLT-4, HL-60 and A-549 cells with IC50 ranging between 2.3-3.1µm [57] . Many mechanisms explained the antimicrobial behavior of many anti-infective drugs such as prevention of nucleic acid, protein and cell wall synthesis, inhibition of functional cell membrane, as well as interfering with many metabolic processes [61] [62] [63] . Herein, molecular modelling was performed on six proteins which were downloaded from the protein data bank and are considered essential for growth, division, the survival of microbes and in the development of resistance using C-docker protocol [64] [65] [66] Table 2 ). The tight fitting of fumigatoside E can be interpreted by the virtue of formation of many tight bonds and interactions within the active sites ( Figure 11 ). • Mild cytotoxic activity against HL-60 cells [28] Many mechanisms explained the antimicrobial behavior of many anti-infective drugs such as prevention of nucleic acid, protein and cell wall synthesis, inhibition of functional cell membrane, as well as interfering with many metabolic processes [61] [62] [63] . Herein, molecular modelling was performed on six proteins which were downloaded from the protein data bank and are considered essential for growth, division, the survival of microbes and in the development of resistance using C-docker protocol [64] [65] [66] . Among all the examined compounds only fumigatoside E (28) showed the best fitting within the active sites of all examined proteins as evidenced by its free binding energies (∆G) that are equal to −14.18, −18.16, -5.02, −20.31, −10.84 and −17.59 Kcal/mol for DNAgyrase, topoisomerase IV, dihydrofolate reductase, β-lactamase, transcriptional regulator TcaR and aminoglycoside nucleotidyl transferase, respectively. It showed in this aspect a superior activity comparable to levofloxacin and moxifloxacin, the potent DNA-gyrase, topoisomerase IV inhibitors, respectively with ∆G = −9.89 Kcal/mol for levofloxacin and −10.19 Kcal/mol for moxifloxacin, respectively whereas aspergicin (150) showed slight fitting. All of the other tested compounds showed unfavorable interaction within the active sites of the examined proteins manifested by the positive values of their free binding energies (∆G) ( Table 2 ). The tight fitting of fumigatoside E can be interpreted by the virtue of formation of many tight bonds and interactions within the active sites ( Figure 11 ). Within the active site of DNA-gyrase, fumigatoside E formed two conventional Hbonds, a π-π bond, three π-alkyl bonds in addition to one C-H interaction and many Van der Waals interactions ( Figure 11A ). Regarding topoisomerase IV, fumigatoside E forms one conventional H-bond, three π-π bonds, two π-alkyl bonds in addition to many Van der Waals interactions and π-cation interaction with the amino acid residues at the active site ( Figure 11B ). Meanwhile, it forms five conventional H-bonds with Gly75, Ala76 and Ala73, two πsulphur and one alkyl interactions with Met72 in addition to many Van der Waals interactions at dihydrofolate reductase active site ( Figure 11C ). Besides, fumigatoside E forms two H-bonds with Lys87 and Asp255, two π-cation interactions with Arg187 and four π-alkyl bonds with Ile117 at β-lactamase active site ( Figure 11D ). Concerning transcriptional regulator TcaR (protein), fumigatoside E forms two H-bonds with Gln 61 and His 42, and five πalkyl bonds with Ala38, Ala24 and His42 and many Van der Waals interactions with the amino acid existing at the active site ( Figure 11E ). Three H-bonds with Asp46, Asp86 and four π-π interactions with Tyr74, Tyr132 and Tyr134 are formed between fumigatoside E and active site of aminoglycoside nucleotidyl transferase ( Figure 11F ). The notable binding of fumigatoside E with DNA-gyrase and topoisomerase active sites IV could greatly interpret its mode of antimicrobial via potent inhibition of both enzymes. COVID-19 infection relies upon host cell factors as Angiotensin-Converting Enzyme 2 (ACE2). The entrance of coronaviruses within the host cell is accomplished by the effective binding of the viral spike (S) proteins to cellular receptors that facilitate their cell entrance, viral attachment to the surface of target cells with subsequent infection triggering. SARS-S engages angiotensin-converting enzyme 2 (ACE2) as the entry receptor in which SARS-S/ACE2 interface was previously elucidated at the atomic level, and the effectiveness to bind with ACE2 was found to be a key determinant of SARS-CoV transmissibility. Thus the prohibition of ACE2 catalytic pocket by bioactive entities could alters the conformation of ACE2 in a manner that it could prohibit SARS-CoV-2 entrance within the host cells through ACE2 [67, 68] . Thus, molecular modelling was performed for the sixteen alkaloids that previously displayed antimicrobial potential on Angiotensin-Converting Enzyme 2 (PDB ID 1R4L; 3.00 A • ) which was downloaded from the protein data bank. Fumigatoside E (28) showed the most fitting within the active sites of ACE2 followed by aspergicin (150) displaying ∆G of −21.17 and −17.66 Kcal/mole, respectively (Table 3) . Table 3 . Free binding energies (∆G) in Kcal/mole of alkaloids isolated from Aspergillus and showed anti-infective potential using in silico studies on Angiotensin-Converting Enzyme 2 (ACE2). Fumigatoside E (forms many tight interactions with the amino acid moieties at the active pocket of ACE2 represented by one H-bond with Arg273, π-π bond with His 379, three π-alkyl interactions with Pro346 and Phe274 in addition to the formation of two π-cation interactions with Lys363 and Ar273 ( Figure 12A ). Meanwhile, aspergicin forms one H-bond with Arg518, π-π bond with Phe 274, two π-alkyl interactions with His345 and Pro346, C-H bonds with Asn149 and Thr 371( Figure 12B ). Around 174 alkaloid metabolites were reported from genus Aspergillus, 66 of which showed important biological activities with respect to the tested biological activities mainly comprising antiviral, antibacterial, antifungal, cytotoxic, antioxidant and antifouling activities. Besides, in silico studies on different microbial proteins were done for sixteen alkaloids that showed anti-infective potential for better mechanistic interpretation for their probable mode of action. Fumigatoside E showed the best fitting within the active sites of all examined proteins as evidenced by its free binding energies. Additionally, fumigatoside E showed the most fitting within the active sites of ACE2 followed by aspergicin and thus could serve as bioactive candidates for combating SARS-CoV-2 infection. Further studies are to be conducted to examine the biological activities of the additional alkaloids that displayed no activity meanwhile in vitro followed by in vivo studies are to be performed to ascertain the results of molecular modelling. Around 174 alkaloid metabolites were reported from genus Aspergillus, 66 of which showed important biological activities with respect to the tested biological activities mainly comprising antiviral, antibacterial, antifungal, cytotoxic, antioxidant and antifouling activities. Besides, in silico studies on different microbial proteins were done for sixteen alkaloids that showed anti-infective potential for better mechanistic interpretation for their probable mode of action. Fumigatoside E showed the best fitting within the active sites of all examined proteins as evidenced by its free binding energies. Additionally, fumigatoside E showed the most fitting within the active sites of ACE2 followed by aspergicin and thus could serve as bioactive candidates for combating SARS-CoV-2 infection. Further studies are to be conducted to examine the biological activities of the additional alkaloids that displayed no activity meanwhile in vitro followed by in vivo studies are to be performed to ascertain the results of molecular modelling. 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On the root growth of corn (Zea mays L.) Seedlings. Agrochemistry Alkaloidal compounds produced by a marine-derived fungus, Aspergillus fumigatus H1-04, and their antitumor activities. Chin Two new indole alkaloids, 2-(3, 3-dimethylprop-1-ene)-costaclavine and 2-(3, 3-dimethylprop-1-ene)-epicostaclavine, from the marine-derived fungus Aspergillus fumigatus Bioactive novel indole alkaloids and steroids from Deep Sea-derived fungus Aspergillus fumigatus SCSIO 41012 Alkaloids from the marine-derived fungus Aspergillus fumigatus YK-7 and their antitumor activities Aniquinazolines A-D, four new quinazolinone alkaloids from marine-derived endophytic fungus Aspergillus Nidulans Benzodiazepine alkaloids from marine-derived endophytic fungus Aspergillus ochraceus X-ray structures of two stephacidins, heptacyclic alkaloids from the marine-derived fungus Aspergillus Ostianus Speradines BE, four novel tetracyclic oxindole alkaloids from the marine-derived fungus Aspergillus Oryzae Speradines F-H, three new oxindole alkaloids from the marine-derived fungus Aspergillus oryzae Diketopiperazine-type alkaloids from a deep-sea-derived Aspergillus puniceus fungus and their effects on Liver X receptor α Prenylated indole alkaloids from co-culture of marine-derived fungi Aspergillus sulphureus and Isaria felina Indole alkaloids from marine-derived fungus Aspergillus sydowii SCSIO 00305 Study on Indole-Quinazolines Alkaloids from Marine-Derived Fungus Aspergillus sydowi PFW-13 and Their Anti-Tumor Activities Cytotoxic alkaloids and antibiotic nordammarane triterpenoids from the marine-derived fungus Aspergillus Sydowi Speradine A, a new pentacyclic oxindole alkaloid from a marine-derived fungus Aspergillus Tamarii Asperterrestide A, a cytotoxic cyclic tetrapeptide from the marinederived fungus Aspergillus terreus SCSGAF0162 Cottoquinazoline A and cotteslosins A and B, metabolites from an Australian marine-derived strain of Aspergillus versicolor Versiquinazolines L-Q, new polycyclic alkaloids from the marine-derived fungus Aspergillus Versicolor Antifungal new oxepine-containing alkaloids and xanthones from the deep-sea-derived fungus Aspergillus versicolor SCSIO 05879 Alkaloids from the deep-sea-derived fungus Aspergillus westerdijkiae DFFSCS013 Alkaloidal metabolites from a marine-derived Aspergillus sp. fungus Asperginine, an unprecedented alkaloid from the marine-derived fungus Aspergillus sp Isolation and synthesis of misszrtine A: A novel indole alkaloid from marine sponge-associated Aspergillus sp Asperindoles A-D and a p-terphenyl derivative from the ascidian-derived fungus Aspergillus sp. KMM 4676 Golmaenone, a new diketopiperazine alkaloid from the marine-derived fungus Aspergillus sp Prenylated indole alkaloids isolated from a marine-derived fungus, Aspergillus sp Prenylated Indole Alkaloids Isolated from a Marine-Derived Aspergillus sp Notoamide O, a Structurally unprecedented prenylated indole alkaloid, and notoamides P− R from a marine-derived fungus, Aspergillus sp Protuboxepins A and B and protubonines A and B from the marinederived fungus Aspergillus sp. SF-5044 Aspergicin, a new antibacterial alkaloid produced by mixed fermentation of two marine-derived mangrove epiphytic fungi Bioactive indole alkaloids and phenyl ether derivatives from a marine-derived Aspergillus sp. fungus Bioactive pyridone alkaloids from a deep-sea-derived fungus Arthrinium sp. UJNMF0008 Psychrophilin E, a new cyclotripeptide, from co-fermentation of two marine alga-derived fungi of the genus Aspergillus Marine bacterial inhibitors from the sponge-derived fungus Aspergillus sp Cytotoxic compounds from the marine-derived fungus Aspergillus sp. recovered from the sediments of the Brazilian coast Oximoaspergillimide, a fungal derivative from a marine isolate of Aspergillus sp Sydoxanthone C and acremolin B produced by deep-sea-derived fungus Aspergillus sp. SCSIO Ind09F01 Isolation and structure determination of a new diketopiperazine dimer from marine-derived fungus Aspergillus sp. SF-5280 Antituberculosis compounds from a deep-sea-derived fungus Aspergillus sp. SCSIO Ind09F01 New alkaloids and isocoumarins from the marine gorgonian-derived fungus Aspergillus sp. SCSIO 41501 Bis-indolyl benzenoids, hydroxypyrrolidine derivatives and other constituents from cultures of the marine sponge-associated fungus Aspergillus candidus KUFA0062 Seven new prenylated indole diketopiperazine alkaloids from holothurian-derived fungus Aspergillus Fumigatus 13-Dihydroxyfumitremorgin C, fumitremorgin C, and brevianamide F, antibacterial diketopiperazine alkaloids from the marine-derived fungus Pseudallescheria sp A potent lignan from Prunes alleviates inflammation and oxidative stress in lithium/pilocarpine-induced epileptic seizures in rats Induction of apoptosis in human cervical carcinoma HeLa cells by neoechinulin A from marine-derived fungus Microsporum sp Mechanisms of action of antimicrobials: Focus on fluoroquinolones Volatile constituents of Dietes bicolor (Iridaceae) and their antimicrobial activity Volatile oils from the aerial parts of Eremophila maculata and their antimicrobial activity Validation of the antihyperglycaemic and hepatoprotective activity of the flavonoid rich fraction of Brachychiton rupestris using in vivo experimental models and molecular modelling Evidence for the anti-inflammatory activity of Bupleurum marginatum (Apiaceae) extracts using in vitro and in vivo experiments supported by virtual screening New flavonoid glycosides from two Astragalus species (Fabaceae) and validation of their antihyperglycaemic activity using molecular modelling and in vitro studies In silico screening of natural compounds against COVID-19 by targeting Mpro and ACE2 using molecular docking SARS-CoV-2 cell entry depends on ACE2 and TMPRSS2 and is blocked by a clinically proven protease inhibitor Data Availability Statement: Not applicable. The authors declare no conflict of interest.