Antibiotic-potentiation, antioxidant, cytotoxic, anti-inflammatory and anti-acetylcholinesterase potential of Antidesma madagascariense Lam. (Euphorbiaceae)

Antidesma madagascariense Lam. (AM) is used in the treatment and management of a panoply of human diseases. Leaf decoction, acetone extracts and fractions of AM were evaluated for antimicrobial, antioxidant, anti-inflammatory, cytotoxicity and acetylcholinesterase (AChE) inhibitory activity. The antibiotic potentiating activity of crude acetone extract (AE) was assessed against ATCC bacterial strains of Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 25923 using standard antibiotics. Decoction extract showed significant inhibitory activity against Acinetobacter spp. (MIC: 0.25 mg/mL) which had higher inhibitory effect compared to the positive control Streptomycin (MIC: 1.00 mg/mL). Acetone and decoction extracts inhibited the growth of Candida albicans (MIC: 4.00 mg/mL). All fractions of AE showed broad spectrum activity against ATCC and clinical strains (MIC 0.03-4.00 mg/mL). The results of the combination profiles of the AE with Ciprofloxacin, Chloramphenicol and Streptomycin revealed synergistic interactions (FICI ≤ 0.50) against P. aeruginosa. Crude decoction, acetone extract and fractions were found to be potent reducing agent as well DPPH radical scavenger and ABTS cation scavenger. A significant correlation between DPPH, ABTS and total phenolic content (p < 0.05, r = − 0.75 and − 0.82 respectively) was recorded. Three fractions namely DCM:MeOH (85:15) (F5), DCM:MeOH (95:05) (F3) and DCM (F2) [IC50 0.02-0.09 mg/mL] demonstrated significant anti-inflammatory activity as compared to the positive control, diclofenac sodium [IC50 0.18 (0.10-0.31) mg/mL]. AE and its fractions showed AChE inhibitory activities at an IC50 of 35.92-492.6 μg/mL. Cytotoxicity study against Vero cells revealed that AE and hexane fraction were non-cytotoxic while decoction showed cytotoxic effect. Further studies are required to explore the potential of AM crude extracts and fractions as natural source of antimicrobial, antioxidant, anti-inflammatory agents as well as AChE inhibitors.