Bioguided Identification of Active Antimicrobial Compounds from Asphodelus bento-rainhae and Asphodelus macrocarpus Root Tubers

Abstract

Root tubers of Asphodelus bento-rainhae subsp. bento-rainhae (AbR), a vulnerable endemic species, and Asphodelus macrocarpus subsp. macrocarpus (AmR) have traditionally been used in Portugal to treat inflammatory and infectious skin disorders. The present study aims to evaluate the in vitro antimicrobial activity of crude 70% and 96% hydroethanolic extracts of both medicinal plants, specifically against multidrug-resistant skin-related pathogens, to identify the involved marker secondary metabolites and also to assess the pre-clinical toxicity of these medicinal plant extracts. Bioguided fractionation of the 70% hydroethanolic extracts of both species using solvents of increasing polarity, namely diethyl ether (DEE: AbR-1, AmR-1), ethyl acetate (AbR-2, AmR-2) and aqueous (AbR-3, AmR-3) fractions, enabled the identification of the DEE fractions as the most active against all the tested Gram-positive microorganisms (MIC: 16 to 1000 µg/mL). Furthermore, phytochemical analyses using TLC and LC-UV/DAD-ESI/MS techniques revealed the presence of anthracene derivatives as the main constituents of DEE fractions, and five known compounds, namely 7′-(chrysophanol-4-yl)-chrysophanol-10’-C-beta-D-xylopyranosyl-anthrone (p), 10,7′-bichrysophanol (q), chrysophanol (r), 10-(chrysophanol-7′-yl)-10-hydroxychrysophanol-9-anthrone (s) and asphodelin (t), were identified as the main marker compounds. All these compounds showed high antimicrobial activity, particularly against Staphylococcus epidermidis (MIC: 3.2 to 100 µg/mL). Importantly, no cytotoxicity against HepG2 and HaCaT cells (up to 125 µg/mL) for crude extracts of both species and genotoxicity (up to 5000 µg/mL, with and without metabolic activation) for AbR 96% hydroethanolic extract was detected using the MTT and Ames tests, respectively. Overall, the obtained results contribute to the concrete validation of the use of these medicinal plants as potential sources of antimicrobial agents in the treatment of skin diseases.

Pharmacological Studies of Medicinal Potential Phytochemicals in Plant Roots

“…This Special Issue fills the gaps in the current knowledge on the therapeutic potential of phytocompounds that are found in plant roots. In five published original scientific papers, attention has been paid to various aspects of the treatment of diseases, such as chronic kidney disease and bacterial infections, but also a range of biological activities of bioactive root compounds have been studied, including their toxicity on neurobehavioral and reproductive function and inflammatory activity [12][13][14][15][16].…”

“…bento-rainhae and Asphodelus macrocarpus subsp. root tubers with 70% ethanol extract by Malmir et al [15]. The renoprotective effect of Chrysanthemum coronarium L. (Glebosis coronaria (L.) Cass ex.…”