Clinanthus microstephium, an Amaryllidaceae Species with Cholinesterase Inhibitor Alkaloids: Structure-Activity Analysis of Haemanthamine Skeleton Derivatives.

Plants of the Amaryllidaceae family are well-known (not only) for their ornamental value but also for the alkaloids that they produce. In this report, the first phytochemical study of Clinanthus genus was carried out. The chemical composition of alkaloid fractions from Clinanthus microstephium was analyzed by GC/MS and NMR. Seven known compounds belonging to three structural types of Amaryllidaceae alkaloids were identified. An epimeric mixture of a haemanthamine-type compound (6-hydroxymaritidine) was tested as an inhibitor against acetyl- and butyrylcholinesterase enzymes (AChE and BChE, respectively), two enzymes relevant in the treatment of Alzheimer's disease, with good results. Structure-activity relationships through molecular docking studies with this alkaloid and other structurally related compounds were discussed.

Alkaloids from Habranthus tubispathus and H. jamesonii, two amaryllidaceae with acetyl- and butyrylcholinesterase inhibition activity.

Alzheimer's disease (AD) is a neurodegenerative disorder associated with memory impairment and cognitive deficit. Most of the drugs currently available for the treatment of AD are acetylcholinesterase (AChE) inhibitors. Plants of the Amaryllidaceae family are known to synthesize alkaloids, which have shown AChE inhibitory activity. Habranthus tubispathus and H. jamesonii are two Amaryllidaceae that can be found growing wild to the southwest of Buenos Aires in Argentina. Acetyl- and butyrylcholinesterase inhibition was observed for the extracts obtained from bulbs of H. tubispathus and bulbs and aerial parts of H. jamesonii. The strongest cholinesterase inhibition was observed for the alkaloid extract obtained from the aerial parts for H. jamesonii (AChE IC50 = 0.7 microg/mL; BChE IC50 = 6.7 microg/mL). The AChE inhibition observed for H. jamesonii could be explained by the presence of galanthamine and sanguinine, two potent AChE inhibitors. The levels of lycorine and hippeastidine, moderate AChE inhibitors, observed in the bulbs of H. tubispathus could be responsible for the significant AChE inhibition observed. The alkaloids present in these Amaryllidaceae were identified by means of GC-MS analysis. In the case of H. tubispathus, hippeastidine and 3-O-demethylhippeastidine, were isolated and completely characterized by 1H and 13C NMR spectroscopy.

Inhibition of NO production by Grindelia argentina and isolation of three new cytotoxic saponins.

A bioassay-guided phytochemical analysis of the ethanolic extract of Grindelia argentina Deble & Oliveira-Deble (Asteraceae) allowed the isolation of a known flavone, hispidulin, and three new oleanane-type saponins, 3-O-ß-D-xylopyranosyl-(1→3)-ß-D-glucopyranosyl-2ß,3ß,16α,23-tetrahydroxyolean-12-en-28-oic acid 28-O-ß-D-xylopyranosyl-(1→2)-ß-D-apiofuranosyl-(1→3)-ß-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl ester (2), 3-O-ß-D-glucopyranosyl-2ß,3ß,23-trihydroxyolean-12-en-28-oic acid 28-O-ß-D-xylopyranosyl-(1→2)-ß-D-apiofuranosyl-(1→3)-ß-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl ester, (3) and 3-O-ß-D-xylopyranosyl-(1→3)-ß-D-glucopyranosyl-2ß,3ß,23-trihydroxyolean-12-en-28-oic acid 28-O-ß-D-xylopyranosyl-(1→2)-ß-D-apiofuranosyl-(1→3)-ß-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl ester (4), named grindeliosides A-C, respectively. Their structures were determined by extensive 1D- and 2D-NMR experiments along with mass spectrometry and chemical evidence. The isolated compounds were evaluated for their inhibitory activities against LPS/IFN-γ-induced NO production in RAW 264.7 macrophages and for their cytotoxic activities against the human leukemic cell line CCRF-CEM and MRC-5 lung fibroblasts. Hispidulin markedly reduced LPS/IFN-γ-induced NO production (IC50 51.4 µM), while grindeliosides A-C were found to be cytotoxic, with grindelioside C being the most active against both CCRF-CEM (IC50 4.2±0.1 µM) and MRC-5 (IC50 4.5±0.1 µM) cell lines.

Biological activity of essential oils from Aloysia polystachya and Aloysia citriodora (Verbenaceae) against the soybean pest Nezara viridula (Hemiptera: Pentatomidae).

The objective of the current study was to determine the chemical constituents, ovicidal activity, fumigant, contact toxicity and repellent effects of essential oils isolated by hydrodistillation from Aloysia polystachya and A. citriodora against eggs and second instar nymphs of Nezara viridula. The major components were carvone (83.5%) for A. polystachya, and citronellal (51.3%) and sabinene (22.9%) for A. citriodora. The ovicidal activity of both oils was tested by topical application at different concentrations ranging from 1.2 to 12.5 microg/egg; all concentrations had a toxic effect. Data probit analysis showed that the LC50 value for A. polystachya was 2.3 microg/egg and for A. citriodora 1.9 microg/egg. The fumigant activity was evaluated in an enclosed chamber. The toxicity increased with concentration from 11 to 176 microg/mL air, and with exposure times from 1 to 48 h. The LC50 values for A. polystachya and A. citriodora were 29.9 and 13.5 microg/mL air 24 h after treatment, respectively. To evaluate contact activity a glass-vial bioassay was used. The toxicity increased with concentration from 2.8 to 45 microg/cm2 and with exposure time from 1 to 48 h. The LC50 for A. polystachya was 3.4 microg/cm2 and for A. citriodora 8.1 microg/cm2. The repellency bioassay demonstrated that both oils were active at the highest concentration (2.6 and 5.3 microg/mL air) and neutral at 1.3 microg/mL air. These results show that the essential oils from Aloysia polystachya and A. citriodora could be applicable to the management of populations of Nezara viridula.

Antioxidant activity and chemical composition of essential oil from Atriplex undulata.

The essential oil from aerial parts (stems and leaves) of Atriplex undulata (Moq) D. Dietr. (Chenopodiaceae) has been studied for its in vitro antioxidant activity. The chemical composition of the oil obtained by hydrodistillation was determined by GC and GC-MS. The major constituents were p-acetanisole (28.1%), beta-damascenone (9.3%), beta-ionone (5.1%), viridiflorene (4.7%) and 3-oxo-alpha-ionol (2.2%). The antioxidant activity of the oil was determined by two methods: Crocin bleaching inhibition (Krel = 0.72 +/- 0.15) and scavenging of the DPPH radical (IC50 = 36.2 +/- 1.6 microg/mL). The presence of active compounds like p-acetanisole, carvone, vanillin, 4-vinylguaiacol, guaiacol, terpinen-4-ol and alpha-terpineol could explain the antioxidant activity observed for this oil.

Acetylcholinesterase inhibition and antioxidant activity of essential oils from Schinus areira L. and Schinus longifolia (Lindl.) Speg.

The essential oils of Schinus areira L. and S. longifolia (Lindl.) Speg. (Anacardiaceae) have been studied for their in vitro anti-acetylcholinesterase and antioxidant activities. The chemical composition of the oils obtained by hydrodistillation was determined by GC-MS. Fruit and leaf oils of S. areira were analyzed separately. The essential oil from S. longifolia elicited marked enzymatic inhibition (IC50 = 20.0 +/- 1.0 microg/mL) and showed radical scavenger activity (IC50 = 25.2 +/- 2.4 microg/mL). The essential oil from S. areira leaves was more active than that of the fruits in both bioassays.

Antioxidant metabolites from Limonium brasiliense (Boiss.) Kuntze.

A free radical scavenging activity guided fractionation of the polar extract from roots of Limonium brasiliense (Plumbaginaceae) led to the isolation of five active compounds including: myricetin 3-O-alpha-rhamnopyranoside (1), (-)-epigallocatechin 3-O-gallate (2), (-)-epigallocatechin (3), (+)-gallocatechin (4) and gallic acid (5). These and other chemical constituents are reported for the first time for this species. The characterization of these compounds was achieved by spectroscopic methods (1H NMR, 13C NMR and UV).