Research On Pigmentation And Mechanism Of Anthocyanin Synthesis In Plum(Prunus Spp.)Fruits

Chinese plum (Prunus genus) originated in China. The yield and area of plum in China is ranked the first in the world, however, its research works is poor. The main speices cultivated is Prunus salicina Lindl., Prunus domestica Linn., Prunus cerasifera, Prunus Americana March and some hybrids in the world. The skin(?) of plums can be red, purple, blue-black, red, green, yellow or amber, while their flesh comes in hues such as yellow, green and pink and orange-a virtual rainbow. This study was conducted to probe the mechanism of pigmentation and anthocyanin synthesis use different color plums (Prunus salicina Lindl.). A rapid determination method has been developed to elucidate the anthocyanin profiles in plums by high performance liquid chromatography(HPLC).Three enzymes of flavonoid biosynthesis (phenylalanine ammonia-Iyase (PAL ) , chalcone isomerase (CHI )and UDP-glucose:anthocyanidin 3-O-glucosyltransferase (UFGT))were assayed during the development of fruit. Anthocyanin concentration was measured during the same period. The effects of bags, ethylene, temperature and organic acid on anthocyanin synthesis were discussed also. The main results were as followings:Anthocyanin extraction with 5mL methanol(mixed with formic acid to pH 2) soaked for 8 hours at 4℃is the best conditions. Four kinds of stantard anthocyanins were used to detect and 2 of them were found in plum peels. The method was developed for determining anthocyanin content in plum fruits by HPLC. The calibration curves was linear over the range of 0.00104～0.0104mg /mL for cyanin-3-glucoside and cyanin-3-rutiniside, with mean recoveries of 99.5% and 99.25%, RSD 1.98% and 2.5% respectively. All the analyzed showed the same anthocyanin pattern but the different amounts among Chinese plums (Prunus salicina Lindl.), except Richard Early.PAL enzyme activity in Oishi wase was high at 30 days after blossom, followed decreasing with fruit developing then kept rising till ripening and correlated to anthocyanin content during ripening. In immature fruits, PAL enzyme activity in Black Ambar kept increasing and decreasing when fruit reddened. CHI activity in both Oishi wase and Black Ambar showed similar patterns during fruit development, rising at the beginning of pigmentation followed decreasing till mature. In Oishi wase, UFGT increased continuously throughout development and correlated with anthocyanin content during ripening. UFGT in Black Ambar showed indented patterns and there was no relationship between enzyme activity and anthocyanin content. Significant correlation was found between light transmission percentage of bags and fruit pigmentation. A bag of higher light-transmitted has deeper red and the higher a* value in fruit peel. Except for white bag, Bagging with other color brought significant effects on fruit pigmentation as compared to control (non-bagged) except for white bag, though no different effects between with red bag and yellow bag. The most significant effect of bagging on fruit pigmentation was found when using black bag (no light transmitted). Anthocyanin content in peels of mature frult was positively relevant to light intensity, especially when wavelength longer than 580nm(r>0.99*) by bagging. Sugar and organic acid content in sarcocarp were not affected, while the organic acid content in peel, not the sugar content in peel of mature fruit was positively relevant to anthocyanin content(r=0.9815*). Moreover, the activities of PAL and UFGT were also positively relevant to anthocyanin content, with a 0.9613* and 0.9365* correlation coefficient respectively.Anthocyanin can be induced by ethylene at conditions of low sugar level and without light. Different effects of ethylene were observed on different cultivars or different period during fruit development of the same cultivar. PAL and CHI activities increased by ethylene in Fraiar little fruits accompanied anthocyanin synthesis compared to Fulaisuo.The increase of anthocyanin content accompanied by increase of organic acid in peels .Pigmentation of Black Ambar accelerated by external organic acid. Though relationship was observed between anthocyanin and acid contents but it can not be guaranted sufficiently.Anthocyanin synthesis of postharvest plum fruit was closely correlated with temperature. At 0℃, anthocyanin synthesis slowly increased as compared to rapid increase at 20℃. Cyanin-3-glucoside content increased within 10 days while cyanin-3-rutinside decreased at 8^th day in Oishi wase peels. Both anthocyanins increased within 8 days, especially cyanin-3-glucoside, but decreased after eight days in Black Ambar peels at 20℃. No significance was observed in sugar and malic acid contents and pH changes at 0℃. However, malic acid and sugars contents especially fructose and sorbitol were significantly decreased as compared to increasing of pH at 20℃. Those changes were related to anthocyanin synthesis.