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This study aimed to search the α-glucosidase inhibitors from the barks part of Artocarpus elasticus. The responsible compounds for α-glucosidase inhibition were found out as dihydrobenzoxanthones (1–4) and alkylated flavones (5–6). All compounds showed a significant enzyme inhibition toward α-glucosidase with IC50s of 7.6–25.4 μM. Dihydrobenzoxanthones (1–4) exhibited a competitive inhibition to α-glucosidase. This competitive behaviour was fully characterised by double reciprocal plots, Yang’s method, and time-dependent experiments. The compound 1 manifested as the competitive and reversible simple slow-binding, with kinetic parameters k3 = 0.0437 µM−1 min−1, k4 = 0.0166 min−1, and = 0.3795 µM. Alkylated flavones (5–6) were mixed type I (KI < KIS) inhibitors. The binding affinities (KSV) represented by all inhibitors were correlated to their concentrations and inhibitory potencies (IC50). Moreover, compounds 1 and 5 were identified as new ones named as artoindonesianin W and artoflavone B, respectively. Molecular modelling study proposed the putative binding conformation of competitive inhibitors (1–4) to α-glucosidase at the atomic level.

In this study, the inhibitory potential of bacterial neuraminidase (NA) was observed on the leaves of Epimedium koreanum Nakai, which is a popular ingredient in traditional herbal medicine. This study attempted to isolate the relevant, responsible metabolites and elucidate their inhibition mechanism. The methanol extraction process yielded eight flavonoids (1–8), of which compounds 7 and 8 were new compounds named koreanoside F and koreanoside G, respectively. All the compounds (1–8) showed a significant inhibition to bacterial NA with IC50 values of 0.17–106.3 µM. In particular, the prenyl group on the flavonoids played a critical role in bacterial NA inhibition. Epimedokoreanin B (compound 1, IC50 = 0.17 µM) with two prenyl groups on C8 and C5′ of luteolin was 500 times more effective than luteolin (IC50 = 85.6 µM). A similar trend was observed on compound 2 (IC50 = 0.68 µM) versus dihydrokaempferol (IC50 = 500.4 µM) and compound 3 (IC50 = 12.6 µM) versus apigenin (IC50 = 107.5 µM). Kinetic parameters (Km, Vmax, and Kik/Kiv) evaluated that all the compounds apart from compound 5 showed noncompetitive inhibition. Compound 5 was proven to be a mixed type inhibitor. In an enzyme binding affinity experiment using fluorescence, affinity constants (KSV) were tightly related to inhibitory activities.

In this study, the changes in free amino acids of soybean leaves after ethylene application were characterized based on quantitative and metabolomic analyses. All essential and nonessential amino acids in soybean leaves were enhanced by fivefold (250 to 1284 mg/100 g) and sixfold (544 to 3478 mg/100 g), respectively, via ethylene application. In particular, it was found that asparagine is the main component, comprising approximately 41% of the total amino acids with a twenty-five fold increase (78 to 1971 mg/100 g). Moreover, arginine and branched chain amino acids (Val, Leu, and Ile) increased by about 14 and 2–5 times, respectively. The increase in free amino acid in stem was also similar to the leaves. The metabolites in treated and untreated soybean leaves were systematically identified by gas chromatography–mass spectrometry (GC-MS), and partial variance discriminant analysis (PLS-DA) scores and heat map analysis were given to understand the changes of each metabolite. The application of ethylene may provide good nutrient potential for soybean leaves.