ISOLATION AND CHARACTERIZATION OF CYTOTOXIC CONSTITUENTS FROM SOME VOLATILE OIL-CONTAINING MEDICINAL PLANTS

Plants have been recognized for their lifesaving and therapeutic properties. Various forms of cancer are prevalent in the society. Zingiber officinale (rhizome), Eugenia caryophyllus (flower), Callistemon citrinus (leaves), Hyptis suaveolens (leaves), Ocimum basilicum (leaves), Ocimum gratissimum (leaves) as well as Tetrapleura tetraptera pod are used in ethnomedicine in treating tumor-related ailments. This study was undertaken to evaluate the cytotoxic and growth inhibitory effects of these plants using predictive and confirmatory tests on cancer cell lines. Preliminary screening of the essential oils of Z. officinale (rhizome), E. caryophyllus (flower), C. citrinus (leaves), H. suaveolens (leaves), O. basilicum (leaves), O. gratissimum (leaves) and T. tetraptera pod methanol extract was carried out using bench-top assay methods for cytotoxicity involving the use of tadpoles of Raniceps ranninus (10-40 μg/mL) and brine shrimp of Artemia salina (10-1000 μg/mL), and antiproliferation using radicle of Sorghum bicolor seeds (1-30 mg/mL). The essential oils were further tested on breast cancer (AU 565) and cervical cancer (HeLa) cell lines at 50 μg/mL. Essential oils of E. caryophyllus, O. basilicum and O. gratissimum were subjected to column chromatography and preparative TLC and the resulting fractions were also tested. T. tetraptera extract was partitioned into hexane, chloroform and aqueous fractions which were tested against AU 565. Vacuum liquid chromatography and other chromatographic techniques employed in the evaluation of the chloroform fraction led to the isolation of two compounds which were also tested for their effects on AU 565 and MDA- MB231 at 50 μM. The essential oils and their respective isolates were subjected to GCMS while NMR and Mass spectrometric analysis were carried out on the isolates obtained from the extract. The results of the preliminary screening of the essential oils and extract showed a concentration dependent activity. Similar activities were also observed with the tadpole and brine shrimp mortality assays. H. suaveolens and Z. officinale oils showed the highest activity against AU 565 cells with 86.74 and 43% growth inhibitions respectively. The chromatographic procedures on the essential oils resulted in isolates with higher activities. GCMS revealed them to be thymol from O. gratissimum and eugenol from E. caryophyllus which produced +85.07 % and +18.82 % inhibitions against AU 565 cells respectively, as well as estragole from O. basilicum which gave +89.3 % inhibition against HeLa cells. The partitioning and isolation procedures carried out on T. tetraptera pod extract resulted in the isolation of two compounds. NMR and MS revealed the XX compounds to be 22-hydroxyisohopane and (3-O-[β-D-glucopyranosyl-2'-acetamido-2'- deoxy]- oleanolic acid with 14.36 and 19 % inhibitions against breast cancer cell line respectively. These results have shown the potency and justified the probable use of these plants in ethnomedicine in treating tumor-related ailments.