Cytotoxicity and cytochrome P450 inhibitory activities of Clinacanthus nutans.

Clinacanthus nutans Lindau (family: Acanthaceae), also known as "Sabah Snake Grass" or "Belalai Gajah" in Malaysia, has been widely used by Malaysians due to its anticancer property. However, the anticancer activity of C. nutans leaves extract and its safe use need to be further investigated. The objectives of the present study were to evaluate the cytotoxic effects of methanol leaves extract of C. nutans in various human cancer cell lines and to evaluate the in vitro effect of C. nutans leaves on the activity of CYP3A4 and CYP2E1 in human liver microsomes.

The cytotoxic effects of methanol extract of C. nutans leaves in various cancer cell lines (Hep-G2, A549, HT-29, MDA-MB-231, MCF-7, and CRL 1739) and normal cells (3T3) were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell proliferation assay. The activities of CYP3A4 and CYP2E1 were determined using simple spectrophotometric methods.

Results obtained showed that the methanol extract of C. nutans leaves exhibited the highest cytotoxic effect against Hep-G2 cell lines (liver cancer) (IC50=13.33 μg/mL), followed by breast cancer oestrogen negative (MDA-MB-231) (IC50 of 18.67 μg/mL). Methanol leaves extract of C. nutans showed significant inhibition (p<0.05) in CYP3A4 and CYP2E1 activity in human liver microsomes.

In conclusion, methanol leaves extract of C. nutans exhibited the highest cytotoxic activity against liver cancer cells (Hep-G2). There is a possibility that herb-drug interaction could occur with C. nutans through inhibitory effects on CYP3A4. Additionally, inhibition of C. nutans on CYP2E1 could show anti-carcinogenesis effects in human liver microsomes.