Documentation and biological and phytochemical analysis of Chungtia medicinal plants of Nagaland, India

Nagaland is a small State in North-East India. Its Indigenous tribes have a rich plant folklore culture. The Indigenous Bioresources Research Group (IBRG) of Macquarie University have established a collaborative research partnership with Chungtia village, Nagaland, with the objectives of documenting firsthand ethnobotanical plant knowledge of Chungtia village and investigating the chemical and biological properties of selected plants. This study consisted of three interrelated aspects, namely ethnobotanical research, biological studies, and isolation and characterisation of bioactive constituents from Nagaland medicinal plants.An ethnobotanical research of Nagaland medicinal plants used by Chungtia village was conducted with the cooperation of Chungtia villagers. This resulted in the documentation of 135 plants. These plants were taxonomically identified and voucher specimens were deposited at Botanical Survey of India (BSI), Shillong, India, for future reference. Of these 135 plants, 39 plants have been previously reported for similar ethnomedicinal uses elsewhere in Nagaland, 61 plants have been previously reported in Nagaland for different ethnobotanical purposes, and 35 plants appear to have novel ethnomedicinal uses in Nagaland.Thirty five plants were documented for their use in skin related treatments and literature searches on these plants indicated 16 plants with either no antibacterial or phytochemical studies previously reported. This led to the selection of eight plants for antibacterial screening with priority given to those plants that were reported as treatments for skin diseases. Three plants were also selected from the literature on Nagaland medicinal plants for antibacterial activity studies.The antibacterial screenings were performed on 11 plants against three pathogenic microorganisms, i.e. S. aureus, E. coli and P. aeruginosa, by using disc diffusion and MTT microdilution assays. All of the eight plants used by Chungtia villagers showed antibacterial activity against S. aureus, at concentrations less than 2.5 mg/ml. The highest inhibitory activities were exhibited by the stem bark of Erythrina stricta and the roots of Prunus persica, with MIC values of 156 μg/ml and 312 μg/ml, respectively. Based on the antibacterial screening results, the stem bark of E. stricta, root bark of P. persica and root bark of Diospyros lanceifolia were selected for further biological and chemical investigations of their antibacterial constituents.The bioassay guided isolation of the dichloromethane partition of the ethanolic extract of the stem bark of E. stricta led to the isolation of 11 compounds: the flavanones 5-hydroxysophoranone and maackiaflavanone B, the isoflavones chandalone, alpinumisoflavone and lupalbigenin, and the pterocarpans 1-methoxyerythrabyssin II, erythrabyssin II, erystagallin A, phaseollidin, cristacarpin and 2-(γ,γ-dimethylallyl)-6a-hydroxyphaseollidin. This is the first reported isolation of any of these 11 compounds from the stem bark of this plant. The antibacterial activities of the isolated compounds were evaluated against four different strains of S. aureus including two drug-resistant strains. The most potent inhibition was shown by lupalbigenin. Compounds 1-methoxyerythrabyssin II, erythrabyssin II, erystagallin A, cristacarpin and 2-(γ,γ-dimethylallyl)-6a-hydroxyphaseollidin were active against all of the strains.The ethyl acetate fraction of the root bark of P. persica led to the isolation of afzelechin and entepiafzelechin-(2α→O→7,4α→8)-(-)-afzelechin. This is the first report of ent-epiafzelechin-(2α→O→7,4α→8)-(-)-afzelechin isolation from P. persica. The two compounds were tested for antibacterial activities against eight bacteria, including both Gram-positive and-Gram negative bacteria and two methicillin resistant Staphylococcus aureus (MRSA) strains, but they were found to be not active even at a concentration of 250 μg/ml.Examination of the n-hexane fraction of the root bark of D. lanceifolia, which showed activity against S. aureus, E. coli and P. aeruginosa in the disc diffusion assay, led to the isolation of the two antibacterial compounds plumbagin and 7-methyljuglone. Plumbagin and 7-methyljuglone were tested against eight microorganisms including both Gram-negative and Gram-positive bacteria and two MRSA strains to expand the current bioactivity data on these compounds. Plumbagin showed more potent and broad spectrum activity than 7-methyljuglone.