Phenylpropanoid-rich Essential Oils of Piper Species from the Amazon and their Antifungal and Anti-cholinesterase Activities.

The essential oils (EOs) from aerial parts of Piper aduncum, P. callosuin and P. marginatum, collected from the Amazon region of Brazil, were analyzed by GC-MS and then evaluated for their antifungal and anticholinesterase activities. The essential oils were dominated by phenylpropanoids, such as dillapiole (73.0%) in P. aduncum, safrole (66.0%) in P. callosum and 3,4-methylenedioxypropiophenone (21.8%) in P. inarginatum. The analyzed oils showed low to moderate antifungal activity; with detection limits (DL) from 10 to 100 pg against Cladosporium cladosporioides and C. sphareospermum. In the anticholinesterase (AChE) evaluation, the oils of P. callosum (DL = 0.01 ng) and P. marginatum (DL = 0.01 ng) were one hundred times more potent than the standard physostigmine (DL = 1.0 ng). Molecular docking analysis showed that phenylpropanoids docked reasonably well with acetyleholinesterase and may be responsible for the anti-AChE activities of the Piper EOs. This is the first presentation about acetylcholinesterase inhibition by methylenedioxyphenyl-propanoids.

Acetylcholinesterase inhibitory activity and molecular docking study of 1-nitro-2-phenylethane, the main constituent of Aniba canelilla essential oil.

The odoriferous principle of Aniba canelilla (H.B.K.) Mez is due 1-nitro-2-phenylethane, the main constituent of its essential oil and also responsible for the plant's cinnamon scent. This nitroderivative was previously reported by their antioxidant, antinociception, cardiovascular, and vasorelaxant properties, and now it was tested as the inhibitor of acetylcholinesterase using bioautography on TLC plates. The oil and a purified fraction containing 1-nitro-2-phenylethane were analyzed by GC and GC-MS. The percentage content of 1-nitro-2-phenylethane in the oil and after fractionation was 70.2% and 98.0%, respectively. The results showed that the oil and 1-nitro-2-phenylethane are strong acetylcholinesterase inhibitors with the detection limit of 0.01 ng, equivalent to physostigmine used as the positive control. A molecular docking study was used to determine the position and conformation of the 1-nitro-2-phenylethane inhibitor in the receptor-binding pocket of the acetylcholinesterase enzyme. The nitrogroup of 1-nitro-2-phenylethane was positioned near of the catalytic serine residue of acetylcholinesterase, forming strong hydrogen bond with its hydroxyl group. Therefore, the electronegative character of 1-nitro-2-phenylethane may explain the interaction that occurs with the catalytic serine residue and its significant inhibitory activity of acetylcholinesterase.

Essential oil composition of three Peperomia species from the Amazon, Brazil.

The essential oils of three species of Peperomia from the Amazon, Brazil, were hydrodistilled and their 96 volatile constituents identified by GC and GC-MS. The main constituents found in the oil of P. macrostachya were epi-alpha-bisabolol (15.9%), caryophyllene oxide (12.9%), myristicin (7.6%), an aromatic compound (6.6%) and limonene (5.4%). The oil of P. pellucida was dominated by dillapiole (55.3%), (E)-caryophyllene (14.3%) and carotol (8.1%). The major volatile found in the oil of P. rotundifolia was decanal (43.3%), probably a fatty acid-derived compound, followed by dihydro-P3-santalol (9.0%), (E)-nerolidol (7.9%) and limonene (7.7%). The aromatic compounds elemicin, myristicin, apiole, dillapiole and safrole identified in these Peperomia species has been found also in Amazon Piper species. The oils and methanol extracts showed high brine shrimp larvicidal activities. The oil of P. rotundifolia (LC50 = 1.9 +/- 0.1 microg/mL) was the more toxic, followed by the extract of P. pellucida (LC50 = 2.4 +/- 0.5 microg/mL) and the oil of P. macrostachya (LC50 = 9.0 +/- 0.4 microg/mL), therefore with important biological properties.