Dynamic changes of polyphenols and related enzymes activity during the development and maturation of Chinese olive (Canarium album L. )

Abstract: 【Objective】The astringency of phenols affects the quality of fresh fruits. The change of polyphenols in different lines of Chinese olive (Canarium album (Lour.) Raeusch.) fruits and the relationship between polyphenols and enzymes related to phenol metabolism were explored, and the phenol components and key enzymes affecting the fresh eating of fruits were revealed.【Methods】The contents of polyphenols (gallic acid, rutin, ellagic acid, methyl gallate, hyperoside) of common line C. album‘Tantou23'with obvious astringency and C. album‘Makeng 22', a selection for fresh eating from its seedlings with mild astringency, obvious aftertaste, were analyzed by high performance liquid chromatography (HPLC) during fruit development and maturation for studying the dynamic changes of phenolic substances and three phenylpropane metabolic enzymes (PAL, C4 H, 4 CL) and polyphenol decomposition related enzymes (PPO, POD) of phenylpropane.【Results】The contents of total phenols and polyphenols in C. album‘Makeng 22'were lower than those in C. album‘Tantou 23'in ripe fruits. The contents of total phenols, ellagic acid, rutin, hyperoside, methyl gallate and gallic acid in C. album‘Tantou 23'were 1.44, 1.32, 1.57, 1.53, 3.08 and 1.24 times of C. album‘Makeng 22', respectively. Except for gallic acid, total phenol, ellagic acid, rutin, methyl gallate and hyperoside were significantly different (p < 0.01) ; The content of rutin was the highest in C. album‘Makeng 22', followed by ellagic acid, which was slightly lower than rutin, and the content of ellagic acid was the highest in C. album‘Tantou 23'. The total phenol contents of the two lines reached the peak at 102 days after anthesis, and then decreased gradually with fruit maturation. The total phenol content of C. album‘Makeng 22'was significantly lower than that of C. album‘Tantou 23' (p < 0.01) at every stage. Except for gallic acid and rutin, the contents of ellagic acid, methyl gallate and hyperoside in C. album‘Makeng 22'were also significantly lower than those in C. album‘Tantou 23' (p < 0.01) . The change trends of PAL activity in two lines were basically similar, and there was no significant difference in PAL activity at maturity (p > 0.05) . It was suggested that the accumulation of phenolic substances during olive fruit development and maturity might not be related to PAL, which might not be the main cause of the difference in the content of phenolic substances between two lines. The trends of C4 H activity in two lines were also similar. The C4 H activity in C. album‘Makeng22'was significantly lower than that of C. album‘Tantou 23' (p < 0.01) during the whole fruit development and maturity period. Although the change trends of 4 CL activity were different between the two lines, the activity of 4 CL in C. album‘Makeng 22'was lower than that of C. album‘Tantou 23'during olive fruit maturity except for the later stage of fruit development. Therefore, it was suggested that C4 H and 4 CL might be related to the difference of the content of polyphenols between two the lines. There was no significant difference in POD activity between the two lines (p > 0.05) . Although POD activity peaked in C. album‘Makeng 22', which was significantly higher than that of C. album‘Tantou 23', at the later stage of fruit development. But there was no significant difference in POD activity between the two lines during fruit ripening. Therefore, POD might not be the main reason for the difference of fruit flavor between the two lines during fruit ripening, but the difference and influence of POD during fruit development need further to study. The PPO activity in C. album‘Makeng 22'peaked at the later stage of maturation and was significantly higher than that in C. album‘Tantou 23' (p < 0.05) . The PPO activity also decreased as the decrease of polyphenol content. During the olive fruit development and maturation, the pericarp is green, and chlorophyll in the pericarp can be photosynthesized to accumulate nutrients.Therefore, PPO is not only related to polyphenol decomposition, but also may promote polyphenol accumulation by promoting metabolic activity.【Conclusion】The difference of total phenols and polyphenol components result in different bitterness and astringency of common olive and the new selection, and then affect the quality of fresh eating. The difference of ellagic acid, methyl gallate and hyperoside might lead to different taste of fresh-eating Chinese olive. And the coordinated regulation of PPO, C4 H and4 CL results in the difference of the formation of phenols in the two lines of Chinese olive.