Isolation and identification of antibacterial and cytotoxic compounds from the leaves of Muntingia calabura L

Abstract

Ethnopharmacological relevance: Muntingia calabura (Elaeocarpaceae) is one of the most common roadside trees in Malaysia. Its leaves, barks, flowers and roots have been used as a folk remedy for the treatment of fever, incipient cold, liver disease, as well as an antiseptic agent in Southeast Asia. The aim of this study is to isolate and identify the antibacterial and cytotoxic compounds from the leaves of Muntingia calabura L.

Materials and methods: Antibacterial and cytotoxic activities were determined by micro-broth dilution and MTT assays, respectively. Seven fractions (F1-F7), three flavones and a chalcone were isolated from the active EtOAc extract using bioassay-guided screening. The structures of four compounds were elucidated by spectroscopic methods and compared with published data. The compounds were further tested for their antibacterial and cytotoxic activities.

Results: Three flavones and a chalcone [5,7-dihydroxy-3,8-dimethoxyflavone (1), 2',4'-dihydroxychalcone (2), 5-hydroxy-3,7-dimethoxyflavone (3) and 3,5,7-trihydroxy-8-methoxyflavone (4)] were isolated from the active fraction F5 of EtOAc extract. Compounds 1 and 3 were isolated for the first time from Muntingia calabura L. Antibacterial activity indicates that compound 2 exhibited the most significant activity with MIC value of 50 μg/mL and 100 μg/mL against MSSA and MRSA, respectively. Cytotoxic activity indicates that compounds 2 and 3 exhibited very strong activity against HL60 with IC50 values of 3.43 μg/mL and 3.34 μg/mL, respectively.

Conclusion: The antibacterial activity of the leaves of Muntingia calabura L. is ascribable to the active compound 2 while the cytotoxic activity is ascribable to the active compounds 2 and 3.