METHODS: In vitro antioxidant activity was investigated using 2,2'-diphenyl-1-picrylhydrazyl (DPPH), fluorescence recovery after photobleaching (FRAP), and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) methods. The antidiabetic and dermatoprotective effects were studied using enzyme inhibitory activities.
RESULTS: Antioxidant tests showed that PLEO has the best activity (ranging from 29.64 ± 3.04 to 73.80 ± 3.96 µg/mL) compared to its main selected molecules (ranging from 74 ± 3.72 to 107.23 ± 5.03 µg/mL). The α-glucosidase and α-amylase assays demonstrated that the elements tested have a promising antidiabetic potential with IC50values ranging from 78.03 ± 2.31 to 116.03 ± 7.42 µg/mL and 74.39 ± 3.08 to 112.35 ± 4.92 µg/mL for the α-glucosidase and α-amylase assays, respectively, compared to the standard drug. For the tyrosinase test, we found that the EOs (IC50 = 57.72 ± 2.86 µg/mL) followed by limonene (IC50 = 74.24 ± 2.06 µg/mL) and α-pinene (IC50 = 97.45 ± 5.22 µg/mL) all exhibited greater inhibitory effects than quercetin (IC50 = 246.90 ± 2.54 µg/mL).
CONCLUSIONS: Our results suggest that the biological activities of PLEO, as well as its main compounds, make them promising candidates for the development of new strategies aimed at improving dermatoprotection and treating diseases associated with diabetes mellitus and oxidative stress.
METHODS: The aqueous ethanolic leaf extracts of C. caudatus were characterized by NMR and LC-MS/MS. The total phenolic content and α-glucosidase inhibitory activity were evaluated by the Folin-Ciocalteu method and α-glucosidase inhibitory assay, respectively. The statistical significance of the results was evaluated using one-way ANOVA with Duncan's post hoc test, and correlation among the different activities was performed by Pearson's correlation test. NMR spectroscopy along with multivariate data analysis was used to identify the metabolites correlated with total phenolic content and α-glucosidase inhibitory activity of the C. caudatus leaf extracts.
RESULTS: It was found that the α-glucosidase inhibitory activity and total phenolic content of the optimized ethanol:water (80:20) leaf extract of the plant increased significantly as the plant matured, reaching a maximum at the 10th week. The IC50 value for α-glucosidase inhibitory activity (39.18 μg mL- 1) at the 10th week showed greater potency than the positive standard, quercetin (110.50 μg mL- 1). Through an 1H NMR-based metabolomics approach, the 10-week-old samples were shown to be correlated with a high total phenolic content and α-glucosidase inhibitory activity. From the partial least squares biplot, rutin and flavonoid glycosides, consisting of quercetin 3-O-arabinofuranoside, quercetin 3-O-rhamnoside, quercetin 3-O-glucoside, and quercetin 3-O-xyloside, were identified as the major bioactive metabolites. The metabolites were identified by NMR spectroscopy (J-resolve, HSQC and HMBC experiments) and further supported by dereplication via LC-MS/MS.
CONCLUSION: For high phytomedicinal quality, the 10th week is recommended as the best time to harvest C. caudatus leaves with respect to its glucose lowering potential.