PURPOSE: This study provides new insights on the changes of endogenous metabolites caused by I. aquatica ethanolic extract and improves the understanding on the therapeutic efficacy and mechanism of I. aquatica ethanolic extract.
METHODS: By using a combination of 1H nuclear magnetic resonance (NMR) with multivariate analysis (MVDA), the changes of metabolites due to I. aquatica ethanolic extract administration in obese diabetic-induced Sprague Dawley rats (OB+STZ+IA) were identified.
RESULTS: The results suggested 19 potential biomarkers with variable importance projections (VIP) above 0.5, which include creatine/creatinine, glucose, creatinine, citrate, carnitine, 2-oxoglutarate, succinate, hippurate, leucine, 1-methylnicotinamice (MNA), taurine, 3-hydroxybutyrate (3-HB), tryptophan, lysine, trigonelline, allantoin, formiate, acetoacetate (AcAc) and dimethylamine. From the changes in the metabolites, the affected pathways and aspects of metabolism were identified.
CONCLUSION: I. aquatica ethanolic extract increases metabolite levels such as creatinine/creatine, carnitine, MNA, trigonelline, leucine, lysine, 3-HB and decreases metabolite levels, including glucose and tricarboxylic acid (TCA) intermediates. This implies capabilities of I. aquatica ethanolic extract promoting glycolysis, gut microbiota and nicotinate/nicotinamide metabolism, improving the glomerular filtration rate (GFR) and reducing the β-oxidation rate. However, the administration of I. aquatica ethanolic extract has several drawbacks, such as unimproved changes in amino acid metabolism, especially in reducing branched chain amino acid (BCAA) synthesis pathways and lipid metabolism.
EXPERIMENTAL APPROACH: Rhizome and leaves of C. caesia were dried with oven (OD) and freeze (FD)-drying methods, and extracted with different Φ(ethanol,water)=100:0, 80:20, 50:50 and 0:100. The bioactivities of C. caesia extracts were evaluated using in vitro tests; total phenolic content (TPC), antioxidant (DPPH and FRAP) and α-glucosidase inhibitory activity. Proton nuclear magnetic resonance (1H NMR)-based metabolomics approach was employed to differentiate the most active extracts based on their metabolite profiles and correlation with bioactivities.
RESULTS AND CONCLUSIONS: The FD rhizome extracted with Φ(ethanol,water)=100:0 was observed to have potent TPC expressed as gallic acid equivalents, FRAP expressed as Trolox equivalents and α-glucosidase inhibitory activity with values of (45.4±2.1) mg/g extract, (147.7±8.3) mg/g extract and (265.5±38.6) µg/mL (IC50), respectively. Meanwhile, for DPPH scavenging activity, the Φ(ethanol,water)=80:20 and 100:0 extracts of FD rhizome showed the highest activity with no significant difference between them. Hence, the FD rhizome extracts were selected for further metabolomics analysis. Principal component analysis (PCA) showed clear discrimination among the different extracts. Partial least square (PLS) analysis showed positive correlations of the metabolites, including xanthorrhizol derivative, 1-hydroxy-1,7-bis(4-hydroxy-3-methoxyphenyl)-(6E)-6-heptene-3,4-dione, valine, luteolin, zedoardiol, β-turmerone, selina-4(15),7(11)-dien-8-one, zedoalactone B and germacrone, with the antioxidant and α-glucosidase inhibition activities, whereas curdione and 1-(4-hydroxy-3,5-dimethoxyphenyl)-7-(4-hydroxy-3-methoxyphenyl)-(lE,6E)-1,6-heptadiene3,4-dione were correlated with α-glucosidase inhibitory activity.
NOVELTY AND SCIENTIFIC CONTRIBUTION: C. caesia rhizome and leaf extracts contained phenolic compounds and had varies antioxidant and α-glucosidase inhibitory capacities. These findings strongly suggest that the rhizomes of C. caesia are an invaluable natural source of active ingredients for applications in pharmaceutical and food industries.