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ARS Home » Research » Publications at this Location » Publication #123922
Title: METABOLISM OF PHENOLIC COMPOUNDS DURING LOQUAT FRUIT DEVELOPMENT

Author
item DING, CHANG-KUI - ZAAS, SHEJING, CHINA
item CHACHIN, KAZUO - OPU, OSAKA, JAPAN
item UEDA, YOSHINORI - OPU, OSAKA, JAPAN
item IMAHORI, YOSHIHIRO - POU, OSAKA, JAPAN
item Wang, Chien

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Loquat fruit contain high concentrations of polyphenols and high activity of polyphenol oxidase. The fruit tissue turns brown after cutting because of oxidation of the phenolic compounds. Therefore, browning is a problem for fresh-cut loquat as well as for processing into jam, juice, jellies, or canned products. It is important to understand the metabolism of phenolic compounds during loquat fruit development and ripening in order to devise ways to prevent or reduce tissue browning. In the present study, the activity of enzymes responsible for phenolic biosynthesis were investigated and the changes of individual phenolic compounds during fruit maturation and ripening were also examined. Variations of phenolic metabolism among various cultivars were also evaluated. These data are useful for other researchers and for industry interested in reducing browning of loquat for fresh-cut or processing.

Technical Abstract: Phenolic compounds in loquat fruit were identified as 5-caffeoylquinic acid (chlorogenic acid), neochlorogenic acid, hydroxybenzoic acid, 5- p-feruloylquinic acid, protocatechuic acid, 4-caffeoylquinic acid, epicatechin, o-coumaric acid, ferulic acid and p-coumaric acid. Neochlorogenic acid was found to be dominant in early stages of loquat fruit development. Both the concentrations and types of phenolic compounds were high in young fruit, but then decreased steadily during growth. However, the concentration of chlorogenic acid increased during ripening and became predominant in ripe fruit. The large rise in chlorogenic acid concentration appears to be a characteristic of loquat fruit ripening. In all of the cultivars tested, the types of phenolic compounds were similar but the total phenolic content varied from 81.8 to 173.8 mg per 100g fresh pulps. In the biosynthetic pathway of chlorogenic acid, enzyme activities of phenylalanine ammonia-lyase (PAL), 4-coumarate: CoA ligase (CL), and hydroxycinnamoyl CoA: quinate hydroxycinnamoyl transferase (CQT) were high at the early stage of growth and diminished to low levels approximately three weeks prior to harvest, but then rose to a peak at one week before harvest. The changes of these enzyme activities seemed to be associated with variations in chlorogenic acid concentration during development, maturation, and ripening of loquat fruit.