Antioxidant, antiproliferative and antimicrobial activities of the volatile oil from the wild pepper Piper capense used in Cameroon as a culinary spice.

Wild pepper (Piper capense L.f., Piperaceae) is a spice traditionally used in western Cameroon to make soups called 'Nkui' and 'Nah poh'. In the present work, the essential oil hydrodistilled from fruits was analyzed by GC-FID and GC-MS, and for in vitro biological activities, namely cytotoxic, antioxidant and antimicrobial, by MTT, DPPH, ABTS and agar disc diffusion methods. The oil composition was dominated by monoterpene hydrocarbons (56.5%) responsible for the pepper odor, such as (beta-pinene (33.2%), sabinene (10.0%) and alpha-pinene (8.9%). The oil induced a concentration-dependent inhibitory effect on human tumor cells MDA-MB 231 (breast adenocarcinoma), A375 (malignant melanoma) and HCT116 (colon carcinoma), showing IC50 values of 26.3, 76.0 and 22.7 microg/ml, respectively. The oil showed total antioxidant activity with a Trolox equivalent antioxidant concentration (TEAC) value of 140 micromol/g. The essential oil of P. capense proved to be an effective scavenger of the ABTS+ radical, with an activity only about 30 times lower than that of Trolox. Moderate activity was observed against the Gram-positive species Staphylococcos aureus and Enterococcusfaecalis, and the yeast Candida albicans. The notable inhibition of some human tumor cells is worthy of further investigation to discover the possible mechanisms of action responsible for the observed cytotoxic effect of this essential oil.