Phenolic metabolism and lignin synthesis in damaged pericarp of mangosteen fruit after impact Apita Bunsiri a , Saichol Ketsa a, *, Robert E. Paull b a Department of Horticulture, Faculty of Agriculture, Kasetsart University, Chatuchak, Bangkok 10900, Thailand b Department of Tropical Plant and Soil Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa, Honolulu, HI 96822, USA Received 25 March 2002; accepted 7 October 2002 Abstract Firmness and lignin content increased while total phenolics decreased in damaged mangosteen pericarp following impact. The phenolic compounds associated with lignin synthesis in damaged pericarp of mangosteen fruit after impact were separated and identified by UV absorption spectra, thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC) analysis. The phenolic acids unique to damaged pericarp of mangosteen fruit were identified as p -coumaric acid and sinapic acid; p -coumaric acid decreased more rapidly than sinapic acid after impact. p -Coumaric acid and sinapic acid contents in the damaged pericarp of reddish brown mangosteen fruit were greater than those of dark purple fruit, and the sinapic acid content was 20  /40-fold greater than that of p -coumaric acid. The decrease in both p -coumaric acid and sinapic acid in damaged pericarp occurred more rapidly in air than under a nitrogen atmosphere. The results suggest that the incorporation of phenolic acid into lignin was greater in more mature dark purple than less mature reddish brown fruit. # 2002 Elsevier Science B.V. All rights reserved. Keywords: p -Coumaric acid; Damaged pericarp; Firmness; Lignin; Mangosteen fruit; Sinapic acid; Total phenolics 1. Introduction Mangosteen (Garcinia mangostana L.) is native to Malaysia and is widely grown throughout the Southeast Asian countries and the Indian sub- continent. The edible fruit aril is white, soft and juicy with a sweet, slightly acid taste and pleasant aroma (Martin, 1980). It has been reported that the pericarp serves as an excellent packing material to protect the soft aril during transportation (Popenoe, 1974). However, most mangosteen fruit reaches the consumer with some degree of me- chanical injury caused by compression or impact damage resulting in hardening of pericarp (Tong- * Corresponding author. Tel.:  /66-2-579-0308; fax:  /66-2- 579-1951. E-mail address: agrsck@ku.ac.th (S. Ketsa). Postharvest Biology and Technology 29 (2003) 61  /71 www.elsevier.com/locate/postharvbio 0925-5214/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0925-5214(02)00213-2