Effects of Ultraviolet A Supplemented with Red Light Irradiation on Vinblastine Production in Catharanthus roseus

Abstract

Catharanthus roseus produces monoterpenoid indole alkaloids which are a well-known source of drugs (Carter and Livingston, 1976). Especially, vinblastine and vincristine are made from dimeric monoterpenoid indole alkaloids (DIAs) for various cancer chemotherapies. In addition, vindesine and vinorelbine of semi-synthetic alkaloids are used in the same applications as vinblastine and vincristine. DIAs are synthesized via 3’, 4’-anhydrovinblastine, which is synthesized from the coupling of the monomeric precursors, vindoline and catharanthine. Unfortunately, these drugs are very expensive as C. roseus accumulates very low amounts of DIAs in leaves. A coupling reaction of vindoline and catharanthine rarely occurs in nature. Although many researchers have studied total or semi-synthetic techniques for DIAs production by chemical and enzymatic methods (Kutney et al., 1988; Misawa et al., 1988; Kuehne et al., 1991; Yokoshima et al., 2002; Shirahama et al., 2006; Ishikawa et al., 2009), these techniques have not resulted in sufficient benefit. These drugs, derived from DIAs, can still be extracted and purified from large amounts of C. roseus plants, which are cultivated in large fields (Roepke et al., 2010). C. roseus is a perennial plant that is native to subtropical and tropical regions. Optimal temperature for growth of C. roseus plants is between 21 and 27°C (Blazich et al., 1995). In Japan, C. roseus cannot be cultivated continuously throughout the year in outdoor conditions, because the temperature is less than 18°C between November and March. Hence, Japan imports the drugs derived from DIAs. The supply of these drugs might become unstable by weather fluctuation and competition with foreign countries. For the stable supply of these drugs in Japan, it is desirable to produce DIAs domestically. In addition, the regulation system of alkaloid content in C. roseus is influenced by environmental conditions, such as light intensity (Liu et al., 2011; Fukuyama et al., 2015) and nitrogen content in fertilizer (Gholamhoss et al., 2011; Guo et al., 2014). Since it is necessary to control environmental conditions of C. roseus cultivation strictly for stable DIAs production, this cultivation would be preferred to operate in an enclosed environmentally controlled room with artificial lighting, such as a plant factory. We investigate the optimal environmental conditions and cultivation methods to achieve high yield of DIAs using an enclosed environmentally controlled room with artificial lighting. Blue light (B, peak wavelength was 450 nm) and UVA (peak wavelength was 370 nm) light irradiation to multiple shoot cultures or soil-cultured C. roseus plants induced the increase of vinblastine content and the decrease of vindoline and catharanthine content (Hirata et al., 1991; 1992; 1993). On the other hand, the growth of C. roseus grown under monochromatic red light (peak wavelength was 660 nm) irradiation increased compared with light irra-