Abstract
The objective of this study was to determine the impact of development stages of Eucalyptus marginata’s fruits on the fatty acid composition as well as on phenolic, flavonoid, and tannin contents of oils. Taking into account fruit maturity stages, vegetable oils have been evaluated for their biological potentials. Fatty acid profiles were quantified using gas chromatography (GC) coupled to a flame ionization detector (FID). The fatty acid profiles of oils obtained from mature fruits showed highest linoleic acid content (49.21%) and Z-vaccenic (C18:1n-7) + oleic (C18:1n-9) acids (22.40%) and a low content of linolenic acid (C18:3) (1.59%). On the other hand, the major saturated fatty acid compound found in the oil of immature Eucalyptus marginata fruits was palmitic acid (C16:0) with about 27%. Based on the Folin–Ciocalteau method, the obtained results revealed a significant difference in the contents of total polyphenols, flavonoids, and tannins according to the stage of fruit maturity ( p < 0.05 ). Furthermore, the detected antimicrobial potentials were related to the fruit maturity stage. While both veg\etable oils extracted from mature and immature Eucalyptus marginata fruits exhibited notable antibacterial activities against the species Staphylococcus aureus, Enterococcus faecalis, Serratia marcescens, and Escherichia coli, only the oils extracted from immature fruits exhibited an antifungal activity against Candida parapsilosis.
Highlights
Eucalyptus species (Myrtaceae) are fast growing trees exploited for paper pulp and as essential oil sources and ornamental plants [1]
Phenolic Secondary Metabolite Contents. e variation in the phenolic secondary metabolites of the oils prepared from Eucalyptus marginata fruits according to different stages of maturity was evaluated. e obtained results showed a significant difference in the total polyphenolic content according to the stage of maturity (p < 0.05)
These results were not in agreement with previous studies published by Santos et al [12] who claimed that the total phenolic content using EtOH : H2O (50 : 50, v/v) as the solvent was 159.57 ± 6.75 mg gallic acid equivalent (GAE) g−1 of extract; this value is in the range of previously published data for Eucalyptus globulus grown in Portugal [13]
Summary
Eucalyptus species (Myrtaceae) are fast growing trees exploited for paper pulp and as essential oil sources and ornamental plants [1]. Eucalyptus is a native Australian tree, represented by more than 900 species It has been introduced worldwide, including Tunisia [2]. As part of an extensive phytochemical analysis of Eucalyptus marginata L. oils, in literature, no reports have described the fatty acid profiling and biological activities in correlation to the maturity stage. In view of these data, the objectives of this research were to study the impact of maturity stages on (1) the oil yield, (2) total phenol, flavonoid, and tannin contents, (3) fatty acid composition, and (3) some biological potentialities including antioxidant and antimicrobial activities
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