Comparative evaluation of biochemical composition and antioxidant properties of six guava cultivars grown under Tunisian agroclimatic conditions

Guava ( Psidium guajava L.) is recognized for its nutritional value and its content of bioactive compounds associated with antioxidant activity. However, comparative data on cultivar-dependent variability under controlled agroclimatic conditions remain limited, particularly for Tunisian-grown guava. This study investigated genotype-dependent variability in the nutritional composition, phytochemical content, antioxidant activity, and structural characteristics of six guava cultivars cultivated under identical agroclimatic conditions in Tunisia. Proximate composition, vitamin C, soluble sugars, total phenolics, flavonoids, condensed tannins, and carotenoids were determined using spectrophotometric and chromatographic methods. Antioxidant activity was evaluated using DPPH, FRAP, and ABTS assays. Additionally, thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR) were used to characterize thermal behavior and functional groups of freeze-dried fruit powders. Significant differences among cultivars were observed for most biochemical and antioxidant parameters ( p ≤ 0.05). l -49 and RI exhibited comparatively higher vitamin C and total phenolic contents, together with elevated antioxidant activity, whereas HKP and LAL showed higher flavonoid concentrations. PW displayed comparatively greater lipophilic antioxidant activity in the ABTS assay. Pearson correlation analysis revealed positive associations between total phenolics, vitamin C, and antioxidant capacity. Principal component analysis further highlighted cultivar-dependent biochemical variability and distinguished the studied genotypes by their compositional profiles. These findings revealed significant variability among guava cultivars grown under the same environmental conditions and provide useful information for cultivar characterization and future studies related to fruit quality and potential food applications.