Fractionation of an aqueous extract from the aerial parts of Ageratina grandifolia yielded a new natural product, namely, 4-hydroxy-3-((S)-1′-angeloyloxy-(R)-2′,3′-epoxy-3′methyl)butylacetophenone (1), along with eight known compounds, including three flavonoids (2−4) and five chromenes (5− 9). NMR data interpretation and DFT-calculated chemical shifts combined with DP4+ statistical and J-DP4 probability analyses allowed for the complete characterization of compound 1. The presence of compound 1 in a plant that biosynthesizes 2,2dimethylchromenes is noteworthy, because an epoxy derivative has long been postulated as the reaction intermediate from the prenylated p-hydroxyacetophenones to cyclic dimethylchromenes. So far, this key intermediate has not been isolated, due to its purported chemical instability. Thus, this is the first report of a potential epoxide intermediate, leading to any of the chromene constituents of this plant. Compounds 1−9 inhibited yeast α-glucosidase with IC 50 values ranging from 0.79 to 460 μM (acarbose, IC 50 = 278.7 μM). The most active compounds were quercetagetin-7-O-(6-O-caffeoyl-β-D-glucopyranoside (3) and 6hydroxykaempferol-7-O-(6-O-caffeoyl-β-D-glucopyranoside (4). Kinetic analysis of 3 revealed its mixed-type inhibitor nature. Docking studies into the crystallographic structure of yeast α-glucosidase (pdb 3A4A) predicted that 3 and 4 bind at the catalytic site of the enzyme.
An infusion prepared from the aerial parts of Salvia amarissima Ortega inhibited the enzyme protein tyrosine phosphatase 1B (PTP-1B) (IC50~88 and 33 μg/mL, respectively). Phytochemical analysis of the infusion yielded amarisolide (1), 5,6,4′-trihydroxy-7,3′-dimethoxyflavone (2), 6-hydroxyluteolin (3), rutin (4), rosmarinic acid (5), isoquercitrin (6), pedalitin (7) and a new neo-clerodane type diterpenoid glucoside, named amarisolide G (8a,b). Compound 8a,b is a new natural product, and 2–6 are reported for the first time for the species. All compounds were tested for their inhibitory activity against PTP-1B; their IC50 values ranged from 62.0 to 514.2 μM. The activity was compared to that of ursolic acid (IC50 = 29.14 μM). The most active compound was pedalitin (7). Docking analysis predicted that compound 7 has higher affinity for the allosteric site of the enzyme. Gas chromatography coupled to mass spectrometry analyses of the essential oils prepared from dried and fresh materials revealed that germacrene D (15) and β-selinene (16), followed by β-caryophyllene (13) and spathulenol (17) were their major components. An ultra-high performance liquid chromatography coupled to mass spectrometry method was developed and validated to quantify amarisolide (1) in the ethyl acetate soluble fraction of the infusion of S. amarissima.
A decoction prepared from the aerial parts of Melampodium divaricatum showed antinociceptive and antihyperalgesic responses when tested in the formalin model in mice. From the CH2Cl2 fraction of the decoction, two non‐previously reported secondary metabolites, 3‐O‐β‐D‐glucopyranosyl‐16α‐hydroxy‐ent‐kaurane (1) and melampodiamide (2) [(2′R*,4′Z)‐2′‐hydroxy‐N‐[(2S*,3S*,4R*)‐1,3,4‐trihydroxyoctadec‐2‐yl]tetracos‐4‐enamide] were separated and characterized by spectroscopic, spectrometric, and computational techniques. The flavonoids isoquercitrin and hyperoside, which possessed noted antinociceptive properties, were obtained from the active AcOEt fraction of the decoction. The chemical composition of the essential oil of the plant was also analyzed by gas chromatography‐mass spectrometry. The major constituents were (E)‐caryophyllene, germacrene D, β‐elemene, δ‐elemene, γ‐patchoulene, and 7‐epi‐α‐selinene. Headspace solid‐phase microextraction analysis detected (E)‐caryophyllene as the main volatile compound of the plant.
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