Chemical Profiling and Biological Activities of Pelargonium graveolens Essential Oils at Three Different Phenological Stages

The aim of this work was the determination of Pelargonium graveolens (aerial parts) volatile compounds at three developmental stages and the evaluation of their antioxidant, antidiabetic, dermaprotective, anti-inflammatory, and antibacterial effects. The aerial parts of Pelargonium graveolens were collected at three stages, namely the vegetative, beginning, and full flowering. Pelargonium graveolens essential oils were extracted from the dried materials of these aerial parts by hydrodistillation. The volatiles were analyzed by Gas Chromatography-Mass Spectrometry GC-MS, and the antioxidant activity was assessed by DPPH, ABTS, H2O2, and FRAP assays. The in vitro antidiabetic effect was evaluated by the inhibition of α-amylase, α-glucosidase, and lipase enzymes, while the antibacterial activity was assessed against six bacterial strains using an agar well diffusion assay and a microdilution method. The main constituents were menthol, menthene, eremophilene, isoborneol, isogeraniol, α-pinene, linalyl acetate, and 3-carene, with quantitative differences at the three phenological stages. The essential oil at the full flowering stage showed the best antioxidant activity, with IC50 values of 83.26 ± 0.01, 116.42 ± 0.07, 132.25 ± 0.11, and 48.67 ± 0.04 μg/mL for DPPH, FRAP, ABTS, and H2O2 assays, respectively. This oil also exhibited significant effects against α-amylase (IC50 = 43.33 ± 0.01 μg/mL), α-glucosidase (IC50 = 19.04 ± 0.01 μg/mL), lipase (IC50 = 24.33 ± 0.05 μg/mL), 5-lipoxygenase (IC50 = 39.31 ± 0.01 μg/mL), and tyrosinase (IC50 = 124.49 ± 0.07 μg/mL). The essential oil extracted at the full flowering stage showed the best antibacterial effect against a panel of microorganisms with diameter inhibition zones ranging between 11.00 ± 0.17 mm and 17.30 ± 0.17 mm and MIC values from 0.25% to 2% v/v. Overall, the results presented here suggest that the full flowering stage is the best optimal harvest time of Pelargonium graveolens for food and pharmaceutical applications.