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.