Nutrient Compositions, Antioxidant Capacity and Biological Activities of Five-finger Tree (Averrhoa carambola) Stem bark, Root, Leaf and Fruit

Abstract

Averrhoa carambola (star fruit) is widely used in traditional medicine, yet comparative studies on the nutrient composition and bioactivities of its different parts remain limited. This study investigated the nutrient composition, antioxidant capacity, and antibacterial activity of A. carambola fruit, leaves, stem bark, and roots. Proximate and mineral analyses were conducted using standard methods. Total phenolic (TPC) and flavonoid (TFC) contents, DPPH and FRAP antioxidant activities, were determined spectrophotometrically. Antibacterial activity of the stem bark crude ethanol extract, butanol fraction (BF), and aqueous fraction (AF) was evaluated against clinical isolates using agar well diffusion, with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) determined by broth dilution. Results showed higher ash content in roots (6.52%) and leaves (6.04%), while crude fat was highest in roots (6.84%). TPC was 38.21 mg GAE/g (stem bark) and 28.18 mg GAE/g (leaves); TFC was 639.00 mg QE/mg (stem bark). Stem bark extract exhibited superior DPPH (IC₅₀ = 20.25 µg/mL) and FRAP (38.21 µg/mL) activities compared to ascorbic acid. Mineral analysis revealed high levels of K, Ca, and Mg across all parts, though elevated Cr, Pb, and Cd concentrations raise safety concerns. The BF and crude extract demonstrated potent antibacterial activity (MIC = 25 mg/mL; MBC = 50 mg/mL), surpassing imipenem against several isolates. GC-MS analysis identified stigmasta-3,5-diene, catechol, and fatty acids as major compounds. These findings suggest that A. carambola stem bark possesses promising antioxidant and antibacterial properties, supporting its therapeutic potential, though heavy metal contamination warrants caution about consumption.