Differentiation-inducing effect in human colon cancer cells of essential oils

155 A. Rattanamaneerusmee et al. flowers, fruit, seeds, barks, and roots of plants. Essential oils are quite popular worldwide and have been used for consumption and aromatherapy. There is little evidence on essential oils and colon cancer although many researchers have reported on their anti-inflammatory activities12,14. Some studies have been reported on antiproliferative activity of Thai essential oil15. Interestingly, Thai edible plants that can also produce essential oils such as citronella (Cymbopogon nadus L.), holy basil (Ocimum tenuiflorum L.), sweet basil (Ocimum basilicum L.), clove (Syzygium aromaticum L.), lime (Citrus aurantifolia (Christm. et Panz.) Swing), kaffir lime (Citrus hystrix L.), hairy basil (Ocimum americanum L.), lemongrass (Cymbopogon citratus (DC.) Stapf), Galangal (Alpinia galanga L.), guava (Psidium guajava), betel vine (Piper betle L.), lesser galangal (Boesenbergia rotunda (L.) Mansf.), and turmeric (Curcuma longa L.). Thai edible plants used in folk medicines have been reported on many biological activities related to cancers. Citronella oil has been reported on cytotoxicity in human breast cancer (MCF-7) and non-tumorigenic (Vero) cell line. Holy basil oil has been reported an ability to prevent fibrosarcoma tumors induced by 20-methylcholanthrene which acted by increasing the level of endogenous antioxidants in Swiss albino mice. Citronella, sweet basil, lemongrass, turmeric, kaffir lime, betel vine, hairy basil and guava leaf oils demonstrated anti-proliferative activity on human mouth epidermal carcinoma (KB) and murine leukemia (P388) cell lines. Moreover, clove oil also showed cytotoxicity effect on breast cancer (MCF-7 and MDA-MB-231), prostate cancer (DU-145), cervical cancer (HeLa), and esophageal cancer (TE-13) cell lines15,16. Although several essential oils have been reported on biological activity related to cancers, there are no present data on the essential oils on colorectal cancer. Hence, this study was aimed to examine chemopreventive activity of essential oils which were usually used for flavoring and fragrance. 2. MATERIALS AND METHODS 2.1. Plant essential oils and chemicals All plant essential oils were purchased from Thai-China Flavours and Fragrances Industry Company, Limited. The plant essential oils were from (Table 1): citronella (Cymbopogon nadus L.), holy basil (Ocimum tenuiflorum L.), sweet basil (Ocimum basilicum L.), clove (Syzygium aromaticum L.), lime (Citrus aurantifolia (Christm. et