key: cord-0949770-z6mdwmr2 authors: Bhattacharyya, N.; Sarma, S. title: Assessment of availability, ecological feature, and habitat preference of the medicinal herb Houttuynia cordata Thunb in the Brahmaputra Valley of Assam, India date: 2008-12-24 journal: Environ Monit Assess DOI: 10.1007/s10661-008-0694-7 sha: 6e9f45e8ed2f2faec24918941f8efc8ac5fb4ce8 doc_id: 949770 cord_uid: z6mdwmr2 Houttuynia cordata Thunb. is a rhizome-bearing aromatic medicinal herb and is restricted to specialized moist habitats. The plant is collected from natural habitats for local consumption and trade. The status of the species and its variations in physiological performance in different habitats were studied in selected sites of geographically different areas of Brahmaputra valley in eastern India. The surveys were conducted in two different growth stages of the plant during 2005–2007. The sites where the species was encountered were marked and a distribution map was prepared. The frequency and density of the plant was higher in the moist habitats with higher organic carbon (0.85 ± 0.05%). Generally, the density, biomass production and growth had significant (P < 0.05) positive relationship with the soil physicochemical properties (linear curve fit). Soil moisture was the most dependent factor for the plant growth and the optimum growth was recorded at 78 ± 5.6% (r(2) = 0.9; P ≤ 0.01). The physiological performance of the plant in all the studied sites were significantly varied (P < 0.05). The growth and development of H. cordata were also different in the flowering and senescence stages. Clay loam soil, average soil pH of 5.9, and 78% soil moisture were the favorable soil characteristics for the better growth of H. cordata and, hence, these data may be considered for conservation of the species. Houttuynia cordata Thunb (Magnoliophyta: Magnoliopsida: Magnoliidae: Piperales: Saururaceae; Watson and Dallwitz 1992) is the single species of the genus and is native to Japan, South-East Asia, and Himalayas. H. cordata is an aromatic medicinal herb with creeping root stock; leaves broad, ovate-cordate; flowers naked in dense spikes, subtended by four white and petalloid bracts (Bora 2001) . The root, young shoots, leaves, and sometimes the whole plant is traditionally used to cure various human diseases throughout South-East Asia. H. cordata, the well-known traditionally used Chinese medicinal material in China and Japan is listed in the Chinese Pharmacopoeia (The Pharmacopoeia Committee of China 2005). Flavonoids, having a wide range of pharmacological activities, including anti-leukemic, antioxidative, anti-mutagenic, anti-inflammatory, and anti-viral effects as well as the ability of promoting immunologic activity, are considered as one kind of the effective components of H. cordata (Zhang et al. 2008) . In Indo-China, the entire plant is considered for cooling, resolvent, and emmenagogue. The leaves are recommended for measles, dysentery, and gonorrhea and are used in the treatment of eye troubles, skin diseases, hemorrhoids, and in certain diseases of women. Some recent findings on its medicinal properties are antiinflammatory (Lu et al. 2006) , anti-allergic (Kim et al. 2007) , virucidal (Chiang et al. 2003) , antioxidative (Ng et al. 2007) , and anti-cancer (Chang et al. 2001; Kim et al. 2001 ). On steam distillation, the plant yields a light brown essential oil with a strong, somewhat disagreeable odor (Sarkar 1993) . About 22 different components were identified in the essential oil, among which n-decanoic acid (11%), α-terpineol (13%), β-myrcene (4%), 1-decanol (4%), and methyl nonyl ketone (35%) were the major components (Lu et al. 2006) . Recently, during the period of SARS outbreak, H. cordata was one of the ingredients in the SARS prevention formulae recognized by the Ministry of Public Health and the State Administrative Bureau of Traditional Chinese Medicine [TCM] (2003) . H. cordata exhibited significant inhibitory effects on SARS-CoV 3C-like protease (3CLpro) and RNA-dependent RNA polymerase (RdRp) which was non-toxic to laboratory animals following oral administration at 16 g/kg (Lau et al. 2008) . The steam distillate of fresh H. cordata could inhibit herpes simplex virus type-1 (HSV-1), influenza virus, and human immunodeficiency virus type-1 (HIV-1) without showing cytotoxicity (Hayashi et al. 1995) . Traditionally, the aerial portion was used as the medicinal part; however, the root portion has also been included recently as an additional usable part in the Chinese Pharmacopoeia (The Pharmacopoeia Committee of China 2005). Due to its remarkable medicinal properties of H. cordata in traditional reports, GC-MS fingerprinting has already been undertaken for the characterization and identification of organic compounds. About 16 chemical components have been identified by GC-MS fingerprinting from 31 samples collected from various regions of China (Meng et al. 2005) . This kind of approaches unravel the pharmacological potential of H. cordata, which will lead to the use by modern pharmaceutical companies for the production of more efficient drugs against various diseases in the near future. Along with such positive directions, there are some negative aspects regarding the conservation of the plant and its unique genetic pool. The World Health Organization estimates that some 80% of the developing world relies on traditional medicines and out of these, 85% people use plants or their extracts as the active substance (Sheldon et al. 1998) . In India, approximately 2,000 drugs are of plant origin (Dikshit 1999) . Present rapid socio-economic changes and several years of unregulated collection of the valuable medicinal plant species have resulted in the depletion of their populations and habitats in nature. Many of them have become rare and endangered and some species are on the verge of extinction (Kala 2000) . About 20-25% of existing plant species in India have become endangered (Laloo et al. 2006) . Ours is an era of profound changes on the surface of earth, driven by an unprecedented level of human demands on the resources of our planet (Gadgil et al. 1986 ). Degree of threat to natural populations of medicinal plants has increased, because more than 90% of the medicinal plant raw materials of Indian and export herbal industries are drawn from natural habitats (Dhar et al. 2002) . Over 70% of the plants collected by the pharmaceutical industries involve destructive harvesting. These patterns of use possess a definite threat to the genetic stock and to the diversity of medicinal plants. Threat assessment exercises as per latest IUCN guidelines for Southern and Northern India has already listed around 200 species of medicinal plants that are rare, endangered, and threatened. It is necessary to bear in mind that, even if a particular variety of a plant is put under several million hectares of active cultivation, the species can still go extinct in the wild if its wild populations with all their inherent intra-specific diversity is not conserved. It is an established fact that the evolution of the species depends on diversity (Shankar and Ved 2003) . But we can not deny the importance of uninterrupted supply of essential medicinal plants for the existence of pharmaceutical companies for the sake of public health. So the only way to restore human health as well as to decrease overexploitation is to encourage sustainable and discrete collection of medicinal plants from the wild. For this purpose, knowledge about distribution and ecological feature of the plants are necessary. Many plant species still have not been categorized and placed properly in the Red Data Book (RDB) of Indian plants and Conservation Assessment and Management Plan (CAMP) workshops because of inappropriate investigations, lack of ecological data, and subjective classification. Categorization of rare species in RDB has been based on herbarium collections rather than population estimation in the wild and assessment of rare species by few experts in CAMP are the major shortcomings of these documents. Moreover, in CAMP workshops, only few species are assessed, mainly those placed before experts and most species are still non-assessed. Thus, it does not provide full information on the number of taxa under threat for a specific area (Kala 2000) . Presently, no quantitative information on availability in different populations of H. cordata is available in India, especially in Bhramaputra valley of Assam. But various tribes of Assam have been utilizing the plant as a vegetable as well as in various medicinal purposes traditionally (Sarkar 1993; Bora 2001) . Quantitative information on a species plays a vital role in formulating a conservation plan and in understanding the ecology of the species (Uniyal et al. 2002) . Therefore, the present investigation has been attempted to provide quantitative details of H. cordata through (1) assessment of the distribution pattern and (2) analysis of variations in biomass among natural populations in different places. The studied sites . All these five sites were geographically different with foothills to marshy lands, dry lands, urban, and flood-affected areas. These sites also represent the lower, middle, and upper part of the state. The state experiences a very hot-humid weather during summer with an average temperature of 30 • C (max. 38.5 • C. min. 7 • C). The annual rainfall ranges between 1,500 and 2,600 mm with moderate humidity (75%). A large part of the districts is covered by forest under a constant threat of denudation and deforestation because of the large felling of trees for timber, firewood, and annual flood. The physico-chemical characteristics of soil differ from place to place. Because of the diverse climatic, topographic conditions and abundant rainfall, Assam forests support a vast variety of floral and faunal biodiversity. In each population of H. cordata, one 20 × 20 m 2 plot was selected and ten numbers of 1 × 1 m 2 quadrates were placed randomly inside the plot. All the plant species were recorded from the quadrates. The habitat soil characteristics (soil type, pH, moisture, available NPK, etc.) of each plot were also analyzed simultaneously. The pooled quadrate information for each plot was used to analyze compositional features including frequency (F), density (D), abundance (A), and abundance-to-frequency ratio (A/F) (Misra 1968 ). All the populations were visited during the active growing season, i.e., flowering stage (April to July 2006) as well as in senescence stage (November-February 2006 for plant height and biomass estimation. Ten individuals from each population were selected randomly to measure the height of the aerial part of each individual at both flowering and senescence stages and their average heights were determined for each population and among all populations at both stages. One randomly selected individual from each population was harvested at two growth stages [flowering (FL) and senescence (S)]. The harvested individuals were carefully washed to remove soil content and, later, the water adhered to the root surface was removed by pressing the plant carefully onto tissue paper. Thereafter, the entire sample was oven dried at 80 • C to a constant weight. Attempts were made to determine the biomass in the two growth stages to identify the best stage for optimum and sustainable harvest. Biomass (above ground, below ground, and total) was obtained by multiplying individual dry weight with the stand density of the species at each stage (Airi et al. 1997 ). Soil samples were collected from each studied areas. About 500-600 g of soil was collected from the rhizosphere (6 cm soil depth) of H. cordata at the sampling locations. The samples were air dried and packed in perforated polythene bags and were stored at room temperature (25-28 • C) until further analysis. Soil texture and classification were done by the method of Piper (1944) . Soil pH was determined for four replicates per sample. A soil suspension was prepared by stirring a mixture of air-dried soil (sieved through No. 8 mesh) and deionized water: 20% (w/v), for about 20 min. Soil pH was measured by the electrometric method using an Orion digital pH meter. Walkly and Black's Rapid Titration Method was used to determine soil organic matter and other macro elements in the soil (Jackson 1973) . All the data presented are the mean of replicates. The data were analyzed by Microsoft Excel program and an ANOVA was made on the height and biomass of the plant in different growth stages. A linear regression was also made (y = a + b × x) to find the best fit value and the linear curve with soil characteristic and plant growth and biomass. Linear regression, graphs, and diagrams were presented with the help of statistical software program Origin 7.5. Almost all the populations of H. cordata were observed in shady and well-moistened places under the canopy of horticultural trees or in the garden fencing sides. Oxalis corniculata, Cynodon dactylon, Centella asiatica, Nustertium sp., Colocasia sp., Evolvulus sp., Cyperus sp., and Elusine sp. were the common associates of H. cordata. The density of H. cordata was higher in all populations and ranged between 57.3 ± 2.4 (NL) and 101.0 ± 6.4 (JR). The relative contribution of the species to overall stand density was higher than other dicotyledonous herbaceous associates and was comparable to the dominant grass species. The frequency of occurrence was also higher (100%) in all the studied populations (Table 1) . Patterns of A/F ratio were quite different in the sites; however, the average A/F ratio of H. cordata was maximum (n = 5). The distribution of the herb was not common to all the areas and was restricted only to certain pockets in all the studied populations. The average plant height of the medicinal herb showed significant variation (P < 0.05) in flowering and senescence stages. The mean height in flowering stage (considering all populations, n = 5) was 33.86 cm (±5.58), while in senescence stage it was 12.81 cm (±2.76) (Fig. 2) . The average plant height was significantly higher in JR in both the stages (flowering, 40.47 ± 0.77 cm; senescence, 16.31 ± 0.58 cm), followed by DH (36.32 ± 0.49 and 14.32 ± 0.49 cm). While the minimum plant heights were recorded 29.01 ± 0.44 cm (flowering) and 8.96 ± 0.29 cm (senescence) in NL. The stand density of the plant was also the highest in JR (101.0 ± 6.41) and was minimum in NL (94 ± 6.15) ( Fig. 3) and both sites were in the nearby area. The biomass production of the plant was significantly different (P < 0.005) among the populations (Table 2 and Fig. 4) . The biomass production was also different in the flowering and senescence stages. The above ground biomass production was 214.12 ± 8.42 g/m 2 in flowering stage and 82.82 ± 2.31 g/m 2 in senescence stage in JR which was the maximum among the populations. The total biomass production of H. cordata was 296.94 ± 9.51 g/m 2 in the flowering stage at JR. The analysis of variance table of the biomass production in all the populations showed significant result on above ground and total biomass production (P < 0.005) and non-significant result in below ground biomass production. It has been observed that H. cordata was restricted only to certain habitats, although the plant was available in different geographical regions. The soil characteristics were the dependent factors for the growth of H. cortada in all the populations. The plant was only recorded in the moist habitats and therefore the soil physico-chemical properties were analyzed. The performance of H. cordata was maximum in JR where the soil moisture (78 ± 5.6%) and organic carbon (0.85 ± 0.05%) were also higher than other populations ( Table 3 ). The plant growth and soil characteristic had a significant positive correlation except in DH (linear curve fit; Fig. 5 ). Soil moisture was the most dependent factor of the plant growth and the optimum growth was recorded at 78 ± 5.6% soil moisture (r 2 ≥ 0.9; P ≤ 0.01). However, the growth of the plant was not linear in different soil pH, hence, a linear curve was not fitted (r 2 ≤ 0.33; P ≥ 0.1). Higher soil organic carbon also favored the growth of the plant and was adequately linear in studied sites (r 2 ≥ 0.8; P ≤ 0.1). These data may indicate the optimum environmental parameters for the better growth of H. cordata and hence may be considered for conservation of the plant. Again, the area of DH is also well known for the annual heavy flood which may affect on the growth of the species in that area. The clay loam soil with maximum moisture and slightly acidic pH were favorable for growth and development of H. cordata (Fig. 6 ). The high density (57.3 to 101.0 individuals/m 2 ), accompanied by high frequency of H. cordata in the surveyed populations, indicates that the species has a tendency to cover a wide space in a given area and is able to exhibit thick stocking in optimum environmental parameters, although the species was restricted to certain habitats and less-disturbed habitats in the region. This is probably because of lack of overexploitation or extensive harvesting of this medicinal herb, especially from this region. Additionally, the local people generally harvest only the aerial part of the herb to use as vegetable or as raw herbal medicine for various disorders. High density also reveals that the environment and soil quality is favorable for the luxurious growth and thick stocking of the herb in the region. • stand density; height (cm); above ground biomass (g/m 2 ); -♦-organic carbon (g/10 kg). Error bars are the standard deviations From the study, it can be assumed that the region is very much conducive for the in situ conservation and cultivation of the plant, if and when needed in the future. This is justified in view of the fact that luxurious availability, higher abundance and frequency as well as higher density of a species at present time do not pledge anything about its safe status in the near future. This is because of the growing demand of medicinal plants for the pharmaceutical companies. For instance, there was a large-scale commercial exploitation of medicinal plants from various districts of Himachal Pradesh (Sharma 1995) . In parts of Kulu district, 85% of families adjoining the Great Himalayan National Park (GHNP) meet 65-70% of their total annual cash income by medicinal plants trade (Singh 1999) . Over the last decade, there has been a substantial increase in the quantity of medicinal plants sold in the market. About 61 kg of Aconitum violaceum and 1,468 kg of Picrorhiza kurrooa were collected from the entire state in 1988 -1989 (Sharma 1995 , whereas a total of 5,100 kg of A. violaceum and 8,350 kg of P. kurrooa were collected only from GHNP for selling in the market by local communities in 1998-1999 (Singh 1999) . Nearly 25% of the estimated 25,000 species of vascular plants in the world may become extinct within the next 50 years (Raven 1987; Schemske et al. 1994) . Red Lists of threatened plants are important tools for the conservation of threatened species (Berg et al. 1994) . However, comparison between assessments, before and after Rare Lists were formulated, is obscured by different categories and philosophies (Adsersen 1989; Oredsson 1997) . Considering species performance of H. cordata across the populations, the population at JR appeared to be the best with its highest average plant height, biomass (above ground, below ground, and total), and maximum density. Performance of the herb was inferior coming down from upper to lower Assam (JR to NL). This suggests that H. cordata performs better in upper Assam with moist tropical climate. In case of medicinal plants, the time of harvesting is considered critical for the optimum biomass or availability of active constituents. There was a significant variation in the total biomass during the flowering and senescence stages of H. cor-data, which indicates that the flowering or active growing stage was better for maximum biomass harvesting (fresh and dry weight basis). For longterm survival of populations, it is recommended that plants are harvested in the senescence stage when most of the reproductive stages are over (Bhatt et al. 2006 ). Therefore, this study suggests active cultivation of H. cordata in active growing season to cope with its greater demand. Otherwise, extensive harvesting for optimum biomass in active growing season, i.e., in reproductive season, may pose a threat to the existence of the species in future. The most important conservation strategy is the protection of habitats. In some cases, conservationists have no choice but to devise sustainable harvesting techniques for wild populations (Sheldon et al. 1998) , keeping in mind the demand of local people. The present data on species availability status in different populations of Assam will help in understanding the distribution and status of H. cordata, which will consequently help in designing sustainable harvesting strategies, leading to long-term conservation cautions for this species. The present study also recommends the active cultivation of the species in active growing season to decrease the pressure on natural population in reproductive stage to ensure the longterm sustainability of the species in this part of the world. Since the population of JR showed the highest biomass and performance, therefore a detailed study of this population is required to determine the active constituents of H. cordata. However, finer details of the essential oil and active compound availability in two growth stages are also needed with detailed phyto-chemical analysis. The rare plant of the Galapagos Islands and their conservation Population studies on Podophyllum hexandrum Royle-a dwindling medicinal plant of the Himalaya Threatened plant, animal, and fungus species in Swedish forests: distribution and habitat associations Ecological features of a critically rare medicinal plant, Swertia chirayita, in Himalaya Ethnobotany of lower Subansiri District (Nishi Tribe) of Arunachal Pradesh, India Antileukemic activity of Bidens pilosa L. var. minor (Blume) Sherff and Houttuynia cordata Thunb Anti-Herpes simplex virus activity of Bidens pilosa and Houttuynia cordata Current status and future strategy for development of medicinal plants sector in Uttaranchal Biodiversity-northeast India perspectives: people's participation in biodiversity conservation Localities of great significance to conservation of India's biological diversity Virucidal effects of the stem distillate from Houttuynia cordata and its components on HSV-1, influenza virus and HIV Soil chemical analysis (pp. 498) Status and conservation of rare and endangered medicinal plants in the Indian trans-Himalaya Cytotoxic alkaloids from Houttuynia cordata The inhibitory effect of Houttuynia cordata extract on stem cell factor-induced HMC-1 cell migration Status of medicinal plants in the disturbed and the undisturbed sacred forests of Meghalaya, North-East India: population structure and regeneration efficacy of some important species Immunomodulatory and anti-SARS activities of Houttuynia cordata Anti-inflammatory effect of Houttuynia cordata injection Establishment of GC-MS fingerprint of fresh Houttuynia cordata Ecological work book Protective effect of Houttuynia cordata extract on bleomycin-induced pulmonary fibrosis in rats Threatened species not necessarily rare, rare species not necessarily threatened. Environmental Conservation Soil plant analysis (pp. 368) The scope of plant conservation problem world wide Studies on herbaceous plants of Karbi Anglong District of Assam with reference to their taxonomy and economic utilization Evaluating approaches to the conservation of rare and endangered plants A balance prospective for management of Indian medicinal plant Wake-up call for Is using medicinal plants compatible with conservation? Plant Talk A study on the plant community composition and species diversity in Great Himalayan National Park, Western Himalaya State Administrative Bureau of TCM. 11th The Pharmacopoeia Committee of China Current status and distribution of commercially exploited medicinal and aromatic plants in upper Gori Valley The families of flowering plants: description, illustrations, identification and information retrieval. Version: 8th Pressurized liquid extraction of flavonoids from Houttuynia cordata Thunb. Separation and Purification Technology We are thankful to the Principal, Nowgong College, Assam, India for his kind permission and support to carry out our research work. We also thank Mr. M. Chutia, NEIST, Jorhat for his assistance in ecological surveys, statistical analysis, and graphical presentation.