Microwave-assisted extraction and bioactivity evaluation of Morinda lucida stem bark

Abstract

Morinda lucida is widely utilized in ethnopharmacological applications for the management of bacteria-related infectious diseases and oxidative stress-related disorders; however, the validation of its phytochemical profile and bioactivity using microwave-assisted extraction (MAE) remains limited. In this study, MAE was used to obtain ethyl acetate stem bark extract of Morinda lucida (ML-E) which was evaluated for its phytochemical composition, antimicrobial and antioxidant potentials. Extraction of 200 g of the plant material yielded 6.90 g (3.45 %) of extract, dominated by flavonoids (210.99 ± 0.31 mg/ 100 g), anthraquinones (132.43 ± 0.10 mg/ 100 g), triterpenoids (101.97 ± 0.40 mg/ 100 g) and phenolics (65.29 ± 0.00 mg/ 100 g). ML-E exhibited selective activity against methicillin-resistant Staphylococcus aureus (21.33 ± 0.58 mm), Staphylococcus aureus (23.67 ± 0.58 mm), vancomycin-resistant enterococci (26.00 ± 1.00 mm), Klebsiella pneumoniae (22.35 ± 0.58 mm) and Candida albicans (23.67 ± 0.58 mm), with minimum inhibitory concentration of 2.5 mg/mL for all the sensitive organisms except Klebsiella pneumoniae (1.25 mg/mL) and Candida albicans (5.00 mg/mL). Minimum bactericidal/fungicidal concentration ranged from 5.00 mg/mL to 10.00 mg/mL for both bacteria and fungi. ML-E demonstrated concentration-dependent DPPH radical scavenging activity (69.99 % at 500 µg/mL; IC₅₀ = 287.50 µg/mL). Overall, MAE protocol yielded an extract containing measurable bioactive compounds, notable antioxidant potential and selective efficacy against drug-resistant pathogens, supporting its folkloric usage and its potential as a therapeutic precursor.