The lacquer tree, Rhus verniciflua is a deciduous broadleaf tree belonging to the family Anacardiaceae, and the sap thereof is also called a lacquer paint or Lacca Sinica Exsiccata (dried resin of Rhus verniciflua) which is generally used for industrial and medicinal purposes. Particularly, in herbal medicine therapy and folk therapy, Rhus verniciflua has been used as a medicinal material for various applications including treatment of alcohol poisoning, removal or alleviation of fever, expulsion of intestinal parasites, treatment of malaria, and removal or alleviation of abdominal pain, menstrual abdominal pain and constipation, and has also been used as a folk medicine and a healthy food by ingestion of chicken boiled with lacquer tree (Tae-Jung Kim, Korea resource plants (1996), vol. II, pp. 294, published by Seoul National University Press, Seoul, Korea). A variety of research and study has been reported on physiological activity of Rhus verniciflua extracts. For example, it was reported that Rhus verniciflua extracts have antibacterial action, and antioxidant action of flavonoid components and urushiol components found in the sap of the plants (Korean Journal of Food Science & Technology, 31:855-6.3; and Korean Journal of Pharmacognosy 31:345-50). Cytotoxic effects of urushiol components on cancer cells were also reported (Arch. Pharm. Res. 22:638-41 (2000)).
Despite its various physiological activities, Rhus verniciflua has suffered from many limitations in applications thereof for a long period of time, due to the allergy-inducing potential. Owing to many efforts, it was elucidated that the main allergy-inducing agent (allergen) in Rhus verniciflua is urushiol, which has brought about a great deal of approaches and methods to remove urushiol. For example, there may be exemplified a method involving heat treatment of Rhus verniciflua, a method involving solvent extraction of Rhus verniciflua, followed by standing of the extract at a low temperature, and a method involving treatment of Rhus verniciflua with oxygen.
The majority of conventional arts relating to Rhus verniciflua and utilization thereof published hitherto is directed to methods concerning a technology of removing allergenicity, methods concerning pharmacological efficacy of urushiol known as an allergen, pharmaceutical compositions containing the same and preparation thereof, and methods concerning separation and purification of an allergenicity-free Rhus verniciflua extract and pharmacological efficacy thereof.
On the other hand, Rhus verniciflua contains large quantities of antioxidant substances. For example, In-Won Kim, et al have reported isolation of antioxidant substances from Rhus verniciflua bark extracts (Korean J. Food Sci. Technol. 31(3), 855-63 (1999)), and Kye-Taek Lim, et al. have reported that application of a fractionated ethanol extract derived from Rhus verniciflua to brain cells of rats results in strong antioxidant activity (Korean J. Food Sci. Technol. 29, 1248-54 (1997)). Hyung-Jin Jeong, et al. have reported antioxidant power of Rhus species and fractionation method thereof (Korean J. plant. Res. 14(3), 220-8 (2001)). In addition, J.-C. Lee, et al. have reported that the fraction of Rhus verniciflua extract isolated and purified using a silica column exhibits inhibitory effects on the growth of human blood cancer cells (Food and Chemical Technology 42, 1383-88 (2004)). Jung-Chae Lee, et al. have reported a fraction having antioxidant and antimicrobial effects, derived from an ethanol extract of Rhus verniciflua (Food Sci. Biotechnol. 9(3), 139-45 (2000)). Won-Sig Choi, et al. have reported antioxidant effects of components isolated and purified from a methanol extract fraction of Rhus verniciflua and also reported that such a fraction has no significant activity in a cytotoxic test on cancer cells (J. Korean Soc. Agric. Chem. Biotechnol. 45(3), 168-72 (2002)). Kye-Taek Lim has compared and reported preventive effects of hepatocyte apoptosis between a water extract and ethanol extract of Rhus verniciflua (Agric. Chem. Biotechnol. 45(4), 173-9 (2002)). Won-Kyung Cheon, et al. have reported methanol extraction of Rhus verniciflua bark and anti-obesity effects of the extract on obesity-induced mice (Korean Journal of Pharmacognosy vol. 3494, 339-43 (2003)).
Further, as conventional arts directed to the anti-cancer activity of the Rhus verniciflua extract, Korean Patent Application Nos. 1997-00013163 and 1997-0004193 disclose anti-cancer compositions containing urushiol components. Korean Patent No. 0257448 proposes an anti-cancer composition containing fustin, fisetin, sulfuretin and butein, which were obtained by purification of the Rhus verniciflua extract using a silica column. Korean Patent No. 0251526 proposes an anti-cancer composition containing urushiol compounds as main ingredients. Korean Patent Application No. 2002-0018186 proposes Rhus verniciflua extracts having antioxidant effects and apoptosis-preventive effects by allowing ethanol extracts of Rhus verniciflua to stand for some time at a low temperature. Korean Patent Application No. 2002-0071464 proposes therapeutics for treating liver diseases, utilizing Rhus verniciflua extracts. Korean Patent Application No. 2001-0004700 proposes anti-cancer effects of drugs by light-induced ripening and use of an anti-cancer drug utilizing Rhus verniciflua extracts.
The majority of the above-mentioned conventional arts proposes anti-cancer drugs utilizing extracts containing urushiol, fustin, fisetin, sulfuretin, butein, caffeic acid, gallic acid and the like as the main components, by extracting Rhus verniciflua with a solvent including water and purifying the extract via various methods such as column.
However, despite known antioxidant characteristics and anti-cancer activity of Rhus verniciflua extracts, Rhus verniciflua extracts proposed in the above-mentioned conventional arts cannot exert desired levels of anti-cancer activity, thus resulting in failure of practical application thereof as an anti-cancer drug.