Bioactive Composition of Tropical Flowers and Their Antioxidant and Antimicrobial Properties

This study evaluated tropical flower petals' bioactive compounds and antioxidant and antimicrobial properties. The physicochemical characteristics, carotenoids, phenolics, anthocyanins, organic acids, and antioxidant activity of 67 flowers were analyzed. In addition, the antimicrobial activity against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus mutans, Candida albicans, and Candida tropicalis of 35 species was determined. A 2 × 3 experimental design was used for the extraction of carotenoids and phenolics, including solvents and ultrasonic agitation times. The mixture of methanol-acetone-dichloromethane (1:1:2) and acetone-methanol (2:1) resulted in the highest concentration of carotenoids, while acidified 80% methanol favoured phenolic extraction. Renealmia alpinia was extremely rich in carotenoids (292.5 mg β-carotene/g DW), Pleroma heteromallum in anthocyanins (7.35 mg C-3-gl/g DW), while a high content of citric acid was found in Hibiscus rosa-sinensis (17,819 mg/100 g DW). On the other hand, Thibaudia floribunda showed the highest antioxidant activity (7.8 mmol Trolox equivalent/g DW). The main phenolics were m-coumaric acid in Acalypha poiretii (12,044 mg/100 g DW), 4-hydroxybenzoic acid in Brugmansia arborea (10,729 mg/100 g DW), and kaempferol in Dahlia pinnata (8236 mg/100 g DW). The extract of Acalypha poiretii, Brownea macrophylla, and Cavendishia nobilis showed antibacterial activity, while the extract of Pleroma heteromallum was the only one active against Candida albicans. These findings highlight the potential health benefits from certain tropical flowers.