Bioactivity evaluations and phytochemical characterizations of ethanolic extracts from selected mimosaceous plants endemic to Thailand

Abstract

A total of 35 extracts from 20 species of Mimosaceae plants consisted of selected materials as pods, leaves and bark were studied. The biological activities as cytoxicity, antimicrobial, and antioxidant of the ethanolic extracts prepared by successive extraction in soxhlet apparatus were evaluated. Thirteen extracts showed cytotoxicity in the brine shrimp lethality test with the extract of Pithecellobium dulce stem bark was the most toxic (LC50=3.45µg/ml). In the paper disc diffusion method, extracts of Samanea saman leaves (zone inhibition=20.67 ± 0.55 mm) and extract of Archidendron jiringa pericarp (zone inhibition =13.35 ± 0.45 mm) showed the highest growth inhibition against E.coli and S. aureus, respectively. The antibacterial and antifungal activity of Mimosaceae ethanolic extracts were also being evaluated by broth microdilution method. Different results on antibacterial activity from broth microdilution method were obtained compared to the paper disc diffusion method. In the broth microdilution method, extract of Entada rheedii seed coat exhibited the lowest minimum inhibition concentration (MIC) against S. aureus (MIC=0.2 mg/ml) and B. subtilis (MIC=0.1 mg/ml). E. coli showed resistant to most of the extract except for the extract of Cathormion umbellatum (MIC=0.8 mg/ml) and Xylia xylocarpa leaves (MIC=0.8 mg/ml). On the antifungal activity, extract of Samanea saman leaves (MFC=0.25 mg/ml) and Albizzia lebbeck leaves (MFC=2.5 mg/ml) acted as fungicide to Saccharomyces cerevisiae and Candida albicans, respectively in the broth microdilution method. The antioxidant properties of the Mimosaceae plants ethanolic extract were evaluated from the ability to scavenge DPPH radical, scavenge nitric oxide, reducing power and metal chelating ability. The extract of Xylia xylocarpa leaves (IC₅₀ = 0.01±0.001 mg/ml), Albizzia lebbeckoides leaves (IC₅₀ = 2.81±0.15 mg/ml), Cathormion umbellatum leaves (IC₅₀ = 12.0±1.00 µg/ml) and Leucaena glauca twig (IC₅₀ = 1.365±0.034mg/ml) exhibited the highest activity in each antioxidant assays, respectively. In addition, extracts of Archidendron jiringa pericarp and Xylia xylocarpa leaves showed the highest inhibition in the in vitro tyrosinase enzyme inhibition property with L-Tyrosine and L-DOPA as substrates, respectively. The phytochemical content of the extracts were analysed by quantifying the total phenolic content and the analysis with HPLC-PDA. The extracts which showed the highest activity in the biological assays were further characterized by HPLC-ESI-MS. It was plausible that the biological activities of Mimosaceae plants ethanolic extracts were contributed by the tentatively characterized flavonoids glycoside and proanthocyanidins from the extracts.