Fruit cuticular waxes as a source of biologically active triterpenoids

Abstract

The health benefits associated with a diet rich in fruit and vegetables include reduction of the risk of chronic diseases such as cardiovascular disease, diabetes and cancer, that are becoming prevalent in the aging human population. Triterpenoids, polycyclic compounds derived from the linear hydrocarbon squalene, are widely distributed in edible and medicinal plants and are an integral part of the human diet. As an important group of phytochemicals that exert numerous biological effects and display various pharmacological activities, triterpenoids are being evaluated for use in new functional foods, drugs, cosmetics and healthcare products. Screening plant material in the search for triterpenoid-rich plant tissues has identified fruit peel and especially fruit cuticular waxes as promising and highly available sources. The chemical composition, abundance and biological activities of triterpenoids occurring in cuticular waxes of some economically important fruits, like apple, grape berry, olive, tomato and others, are described in this review. The need for environmentally valuable and potentially profitable technologies for the recovery, recycling and upgrading of residues from fruit processing is also discussed.

Keywords: Cuticular waxes; Fruit peel; Health benefits; Triterpenoids.

Fig. 1

Structures of some triterpenoids occurring in apple (M. pumila) fruit cuticular waxes: ursolic acid (1), uvaol (2), 2α-hydroxyursolic acid (3), 3β-trans-cinnamoyloxy-2α-hydroxyurs-12-en-28-oic acid (4), 3β-trans-p-coumaroyloxy-2α-hydroxyurs-12-en-28-oic acid (5)

Fig. 2

Structures of some triterpenoids occurring in grape berry (V. vinifera) fruit cuticular waxes: oleanolic acid (1), oleanolic aldehyde (2), erythrodiol (3), β-sitosterol (4), β-sitosterol-3-O-β–D-glucoside (5), β-sitosterol-6′-linolenoyl-3-O-β-D-glucopyranoside (6)

Fig. 3

Structures of some triterpenoids occurring in olive (O. europaea) fruit cuticular waxes: I maslinic acid, II betulinic acid

Fig. 4

Structures of some triterpenoids occurring in tomato (L. esculentum) fruit cuticular waxes: I α-amyrin, II β-amyrin, III, δ-myrin, IV, lupeol, V, taraksasterol, VI, ψ-taraksasterol

Fig. 5

Structure of friedelin occurring in fruit cuticular waxes of grapefruit (C. paradisi)