Clinical Advances in Anticancer Essential Oils

Abstract

Nutrigenomics has emerged as a key concept and a considerable amount of recent research has been expended in determining the effect of diet on gene expression. A rapidly expanding list of herbal extracts and bioactive ingredients involved in inducing apoptosis have been tested by in vitro and in vivo assays. Encouraging results obtained from preclinical studies have attracted considerable attention, and various phytochemicals have entered clinical trials. Preliminary and early-phase human trials of oral perillyl alcohol administration demonstrated low or moderate treatment response in patients with metastatic adenocarcinoma of colon and rectum, ovarian carcinoma, and various refractory malignancies. Most of the adverse effects of perillyl alcohol were characterized by low-grade gastrointestinal symptoms, which were dose-limiting, although high inter-/intra-patient variability in drug tolerance was observed. Chemoprevention provided by topical application of perillyl alcohol in skin cancer demonstrated borderline changes in UV-damaged skin. Hepatic arterial infusion with embolized curcuma aromatic oil showed promising results in hepatocellular cancer patients. No treatment responses were observed in a phase II study of D-limonene in patients with advanced stages of cancer. The insufficient treatment response could be attributed to a number of factors and might potentially be improved by, for example, overcoming improper drug formulation or low dosage of the active substance. Further clinical trials with improved active substance bioavailability, proper formulation, and better patient randomization are warranted. More importantly, a better understanding of the impact of inherited traits on the response to a specific dietary pattern, functional food, or supplement will be helpful in getting a step closer to personalized medicine.