Background: More than 700 plants are reported to be used for medicinal purposes in Nepal; however, many of them are not studied for their scientific evidences. The aims of the present study were the estimation of the total phenolic and flavonoid contents, and the evaluation of the free radical scavenging and α-amylase inhibitory activities of five selected medicinal plants from western Nepal: Aeschynanthus parviflorus Wall. (Gesneriaceae), Buddleja asiatica Lour. (Loganiaceae), Carica papaya L. (Caricaceae), Drepanostachyum falcatum (Nees) Keng f. (Gramineae) and Spondias pinnata (L. f.) Kurz (Anacardiaceae). Methods: The total phenolic content (TPC) and total flavonoid content (TFC) were measured using Folin-Ciocalteu’s phenol reagent and aluminium chloride methods, respectively. A 1,1–diphenyl–2–picrylhydrazyl (DPPH) free radical scavenging assay was used to evaluate the free radical scavenging activity and an α-amylase inhibitory assay was carried out to determine the in vitro antidiabetic activity. Results: The phytochemical screening of five hydroalcoholic plant extracts revealed the presence of various secondary metabolites, including alkaloids, flavonoids, reducing sugars, saponins, terpenoids and tannins. The amounts of total phenolics and flavonoids were found to be the highest in B. asiatica leaf extract, which also showed the most potent free radical scavenging activity. Extract of C. papaya fruits showed the highest α-amylase inhibitory activity, whereas the extracts of B. asiatica leaves and S. pinnata leaves exhibited moderate activity. Conclusions: Some of the medicinal plants selected in this study showed high TPC and TFC values and potent bioactivities. These results may provide the scientific evidences of the traditional uses of these plants. However, further detailed studies on bioactive compounds isolation and identification and evaluation of in vivo pharmacological activities should be performed in future.

Spondias pinnata (L.f.) Kurz. (family: Anacardiaceae) is a wild deciduous tree indigenous to southeast Asian countries. Different parts of this plant are used traditionally for the treatment and cure of various disorders and illnesses. S. pinnata leaves are used to prevent and treat diabetes in traditional Balinese medicine. However, scientific study on the antihyperglycemic effect of its leaves has not been reported yet. Therefore, this study aims to perform phytochemical screening and investigate the hypoglycemic potential of S. pinnata leaves extract. Preliminary phytochemical screening of the hydroethanolic extract was performed following the standard tests. In vivo hypoglycemic activity of the leaves extract was evaluated using normal and glucose-loaded rats. The results displayed the presence of phytochemical constituents such as saponins, phenolic compounds, flavonoids, and terpenoids. S. pinnata (500 mg/kg) and metformin (100 mg/kg) exhibited a significant ( ) decrease in blood glucose level at 1, 2, and 3 h in normal rats when compared to the control group. Metformin- (100 mg/kg)- and S. pinnata- (500 mg/kg)- treated groups showed a maximum decrease in the blood glucose level at 3 h after single-dose administration in the oral glucose tolerance test (OGTT). In conclusion, S. pinnata leaves possess a significant hypoglycemic activity in the animal model and thus support its traditional use to treat diabetes. Therefore, a detailed mechanism-based study and isolation of bioactive compounds from S. pinnata leaves would be beneficial in the future for the search of new hypoglycemic agents.

Spondias pinnata (L.f.) Kurz.(Anacardiaceae) is widely used as food and medicinal properties. This study aims to disclose the free radical scavenging potential, total phenolic and flavonoid contents and phytochemical constituents of 70% methanol extract of unripe fruits of S. pinnata collected from Kaski district, Nepal. The free radical scavenging activity was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay method. The total phenolic content (TPC) and total flavonoid content (TFC) were estimated by using Folin-Ciocalteu’s phenol reagent and aluminium chloride methods, respectively. S. pinnata fruits extract showed potent free radical scavenging activity with IC50 value 2.75±0.23 μg/ml. TPC and TFC values were found to be 229.24±0.46 mg GAE/g and 192.58±3.81 mg QE/g, respectively. Detailed chemical isolation of the extract afforded caffeic acid methyl ester (1) and rhamnetin 3-O-sophoroside (2). In conclusion, S. pinnata fruits were found to be rich source of phenolic and flavonoid compounds and possessed strong free radical scavenging property. However, further study is needed to explore its potential health benefits and bioassay guided chemical analysis should be performed to isolate and identify the bioactive compounds.

Atropisomeric styrenes remain comparatively underdeveloped because configurational stability about the C(sp ² )C(sp ² ) bond is difficult to achieve and often relies on substantial preinstalled steric congestion. We report a conceptually distinct approach in which atropisomeric styrenes emerge through Diels–Alder reactions of substituted vinylallenes with N ‐methylmaleimide. In these reactions, cycloaddition‐induced geometric and hybridization changes generate a sterically hindered styrenyl atrop‐axis as a direct consequence of bond formation rather than through direct construction of a congested C(sp ² )C(sp ² ) bond. Simultaneously, the reactions generate stereogenic ring junction centers that convert the two orientations about the atrop‐axis into diastereomeric relationships, giving rise directly to distinguishable atropisomeric cycloadducts from achiral precursors. Experimental and computational studies reveal that atropisomerization barriers are governed not simply by steric congestion about the atrop‐axis, but by conformational flexibility of the fused bicyclic framework. Unexpectedly, gem ‐dimethyl substitution at the exocyclic alkene lowers the atropisomerization barrier through ground‐state destabilization arising from enhanced cyclohexene puckering and reduced distortion required to reach the rotational transition structure. Extension of this design principle enabled the preparation of configurationally stable atropisomeric styrenes that could be separated chromatographically and analyzed independently at ambient temperature.