In vitro biological activity of metabolic extracts of wild and cultivated species of the genus Polianthes

Tuberose (Polianthes tuberosa) is the most well-known species of the genus Polianthes. However, the rest of the wild species have been little studied and might possess useful plant secondary metabolites (SM). In this work, extractions of SM from the bulbs of wild and cultivated species of the genus Polianthes were carried out to evaluate their in vitro antimicrobial activity. Extractions with methanol were made from bulbs of P. tuberosa 'Double' and six wild species: P. platyphylla, P. montana, P. clivicola, P. howardii, P. pringlei and the genera Manfreda sp. and Prochnyanthes from the Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco A.C. (CIATEJ) work collection. The bioassays were performed in vitro with the disc diffusion technique (Kirby-Bauer method). The phytopathogens Dickeya dadantii and Pseudomonas aeruginosa were grown in semi-solid agar and poured uniformly onto Petri dishes with Mueller Hinton agar. Filter paper discs were impregnated with 20 μL crude extracts (50 and 100 mg mL^‑1), ciprofloxacin (0.1875 mg mL^‑1) or methanol and placed on the agar surface. The plates were incubated at 37°C for 24 h. All tested extracts inhibited the growth P. aeruginosa; Prochnyanthes extract showed the greatest antibacterial activity, with a percent of inhibition of 24±2.34%. The extracts most effective against D. dadantii were P. pringlei (PI=21.8±2.39%), Prochnyanthes (PI=15.5±0.86%), Manfreda sp. (PI=14.4±1.7%), P. montana (PI=9±1.16%). Extracts, even among those from the same genus, have shown diverse responses, depending on the individual metabolites stored in the bulbs. This study provides the basis for characterization of SM from bulbs of the Polianthes genus with antibacterial activity.