Antimicrobial activity of necklace orchids is phylogenetically clustered and can be predicted with a biological response method

Necklace orchids (Coelogyninae, Epidendroideae) have been used for traditional medicine practices for centuries. Previously carried out bioassays on a subset of unrelated species showed promising antimicrobial, anti-inflammatory, and anti-oxidant activity, providing experimental proof for medicinal properties as recorded in traditional uses. However, none of these species have been investigated ethno-botanically in a phylogenetic context yet. This study aimed to carry out comparative bioprospecting of a group of wild orchids using EBDCS (the Economic Botany Data Collection Standards) organ targeted and biological response methods. Traditional medicinal use of necklace orchids was recorded from books and journals published between 1984 and 2016. Bioassays with a selection of human pathogen microbes were carried out in triplicate on various extractants of leaves and pseudobulbs of Coelogyne cristata and Coelogyne fimbriata cultivated indoors or outdoors. A molecular phylogeny of Coelogyninae based on nuclear ribosomal ITS and plastid matK DNA sequences obtained from 148 species, was reconstructed with Bayesian Inference using MrBayes. Bioprospecting comparison of EBDCS and biological response was carried out using customized R scripts. Ethanolic extracts obtained from leaves of C. cristata and C. fimbriata were found to inhibit growth of Bacillus cereus, Staphylococcus aureus, and Yersenia enterocollitica and confirmed traditional antimicrobial uses recorded in the literature. Leaf extracts were found to have stronger antimicrobial properties for plants cultivated outdoors than indoors. Two hot nodes with high potency for antimicrobial activities were detected for the EBDCS organ targeted classification method whereas four hot nodes were detected for the biological response classification method. The biological response classification method was found to be more effective in uncovering hot nodes leading to clades of species with high medicinal potential as compared with the EBDCS classification method.