In vitro antioxidant activity and cytotoxicity of sequential extracts from selected black pepper (Piper nigrum L.) varieties and Piper species

Present study evaluated in vitro antioxidant activity and cytotoxicity of four important Piper species (P. nigrum L., P. chaba Hunter, P. longum L. and P. colubrinum Link.) and six black pepper varieties (Sreekara, Subhakara, IISR Malabar Excel, Panniyur-1, Panchami and IISR Thevam). It was performed with sequential extracts of the dried berries/fruits using n-hexane, chloroform, methanol and water in the order of increasing polarity. Concentrated extracts were tested for total phenolic content, in vitro antioxidant activity and cytotoxicity. Methanol and chloroform extracts showed high antioxidant activity than hexane and water extracts. Among black pepper varieties, methanol extract of IISR Malabar Excel followed by that of Panchami and among Piper species chloroform extract of P. colubrinum expressed highest antioxidant activity. Significant positive correlation between total phenol and antioxidant activity was noted for methanol and chloroform extracts. In vitro cytotoxicity of the extracts was tested on cervical cancer cell line CaSki by MTT assay and compared with that of synthetic anticancer drug Doxorubicin. Results showed more cytotoxicity with more extract and increased time of exposure with CaSki. Chloroform extract of P. longum and P. colubrinum were found to be highly toxic to CaSki than other extracts. By considering three time intervals, chloroform extract of IISR Malabar Excel was more toxic to CaSki than other black pepper varieties. To the best of our knowledge, this is the first report regarding in vitro antioxidant activity and cytotoxicity on CaSki for sequential extracts of P.colubrinum fruits cultivated in India. This is also the first report on variability in antioxidant activity and cytotoxicity (on CaSki) of sequential extracts from black pepper varieties selected for the study.