Bioactive compounds from Tunisian Pelargonium graveolens (L’Hér.) essential oils and extracts: α-amylase and acethylcholinesterase inhibitory and antioxidant, antibacterial and phytotoxic activities

The phytochemical composition of Pelargonium graveolens L’Her. essential oils and extracts of flowers and leaves and their anticholinesterase, anti-α-amylase, antioxidant, antibacterial and allelopathic potential were investigated. Forty-two volatile components were identified by GC-FID and GC–MS analyses. Citronellol (26.98 %–24.3 %), geraniol (20.65 %–21.81 %) and 10-epi-γ-eudesmol (13.06 %–5.13 %) were the main constituents for leaves and flowers oils. The highest amounts of polyphenols (142.71 mg GAE/g DW), flavonoids (52.32 mg RE/g DW) and flavonols (20.15 mg RE/g DW) were shown by the polar subfraction of the leaf extracts. Flowers were characterized by high levels of condensed tannins (13.27 mg CE/g DW). Essential oils and extracts were found to possess important capacity to inhibit the α-amylase and acethylcholinesterase activities. The oils' and extracts antioxidant activity was relatively high, determined by DPPH (IC50 = 711–1280 μg/mL for oils and 12.24–44.24 μg/mL for extracts) and ABTS (15.8–17.95 μg TE/mg DW for oils and 131.54–241.83 μg TE/mg DW for extracts) assays, which was correlated to their phenolic contents. Based on the determination of the diameter of inhibition and the minimum inhibitory concentration, a high antibacterial activity according to oils and extracts was revealed against eleven bacteria strains. Also, the P. graveolens oils and extracts inhibited the shoot and root growth of Medicago sativa L., Triticum aestivum L. and Lactuca sativa L. seedlings. Therefore, P. graveolens can be used as a natural source of bioactive compounds in food and pharmaceutical industries.