Comparative GC–MS and FTIR profiling with assessment of antioxidant and antimicrobial potential in guava, bay and lemon leaf extracts

This study comparatively explored the chemical composition, antioxidant potential, and antimicrobial activity of methanolic leaf extracts from guava (Psidium guajava), bay (Cinnamomum tamala), and lemon (Citrus aurantifolia) using advanced analytical techniques. Gas Chromatography-Mass Spectrometry (GC-MS) identified the main bioactive substances, including Copaene (13.005 %), Caryophyllene (13.033 %), and 9-Octadecenamide (12.230 %) in guava leaf; phenol,2-methoxy-4-(2-propenyl)-acetate (37.109 %), Benzenemethanol, α-methyl-α-pro- (17.315 %), and 9-Octadecenamide (13.259 %) in bay leaf; and Benzenemethanol, α-methyl-α-pro- (35.369 %), Phenol, 3,5-bis(1,1-dimethylethyl)- (30.733 %), Di-n-octyl phthalate (7.755 %) and 9-Octadecenamide (4.710 %) in lemon leaf. Functional groups such as hydroxyl, carbonyl, and phenolic compounds were confirmed using Fourier Transform Infrared Spectroscopy (FTIR-ATR). Folin-Ciocalteu and aluminum chloride techniques were used to assess total phenolic content (TPC) and total flavonoid content (TFC) respectively. Among the extracts, bay leaf exhibited the highest TPC (192.07 ± 0.79 mg GAE/g), while lemon leaf had the highest TFC (1418.08 ± 2.10 mg QE/g). Antioxidant activity assessed by the DPPH assay demonstrated superior efficacy of bay leaf extract (IC50 = 7.59 ± 0.25 µg/mL) compared to the synthetic standard butylated hydroxytoluene (BHT) (IC50 = 10.63 ± 0.05 µg/mL) where t-test result, p = 0.004 (p < 0.05) indicates statistically significant differences between these two IC50 values. Antimicrobial assays (disc diffusion method) further highlighted the strong inhibitory effects of bay leaf extract against Staphylococcus aureus and Candida albicans. Overall, bay leaf extract exhibited remarkable antioxidant and antimicrobial properties, suggesting its potential application as a natural preservative in food, oil and beverages as an alternative to synthetic preservatives.