Phytochemical Isolation of α-Linolenic Acid from Velvet Apple (Diospyros blancoi) Stem Bark and Assessment of Its Antibacterial, Antioxidant, and Cytotoxic Activities

Abstract

Diospyros blancoi (velvet apple) is a medicinal plant whose stem bark remains relatively underexplored phytochemically. This study aimed to isolate and characterize a major constituent from the chloroform extract of D. blancoi stem bark and to evaluate its antibacterial, antioxidant, and preliminary cytotoxic activities. Fractionation of the chloroform extract by vacuum liquid chromatography followed by preparative thin-layer chromatography yielded compound DB-F7-B1, which was identified as α-linolenic acid based on its ¹H and ¹³C nuclear magnetic resonance spectroscopic characteristics and comparison with reported literature data. The chloroform extract exhibited antibacterial activity against six of nine tested Gram-positive and Gram-negative bacterial strains, with inhibition zones ranging from 8 to 13 mm. The extract contained 11.86 mg gallic acid equivalents (GAE)/g of total phenolics and 4.91 mg quercetin equivalents (QE)/g of total flavonoids. Among the tested fractions, the chloroform-soluble fraction showed the strongest DPPH radical-scavenging activity, with an IC₅₀ value of 41.0 μg/mL, whereas the crude extract exhibited preliminary cytotoxic activity in the brine shrimp lethality assay, with an LC₅₀ value of 3.255 μg/mL. Overall, the findings contribute to the phytochemical characterization of D. blancoi stem bark and demonstrate its preliminary antibacterial, antioxidant, and cytotoxic potential. Further studies involving MIC/MBC determination, bioactivity-guided fractionation, and in vivo evaluation are warranted to establish the therapeutic relevance of its bioactive constituents.