Abstract
Psidium guajava leaves (PGL) have been long used as an adjuvant therapy for diabetics. The present study evaluated the in vivo hypoglycemic and hepatoprotective effects of dried and the rice-fried PGL decoctions (PGLD and RPGLD). Our results indicated that both PGLD and RPGLD could significantly decrease the contents of fasting blood glucose (FBG) and haemoglobin A1c (HbA1c) in diabetic rats. Compared with the HFD/STZ (high-fat diet with streptozotocin) group, the PGLD and RPGLD-treated diabetic rats showed different degrees of recovery against the liver pathological changes. The upregulated expressions of glucokinase (GK), glucose transporter 2 (GLUT2), insulin growth factor-1 (IGF-1), insulin receptor substrate-1 (IRS-1), and insulin receptor substrate-2 (IRS-2) in PGLD and RPGLD-treated groups were observed. In general, RPGLD exhibited a much better antidiabetic effect than PGLD, which was further verified by the comprehensive evaluation with the TOPSIS method. Besides, HPLC (high-performance liquid chromatography) and UPLC-MS/MS (ultra-performance liquid chromatography-tandem mass spectrometry) analyses revealed that the contents of the primary constituents (ellagic acid, hyperoside, isoquercitroside, reynoutrin, guaijaverin, auicularin, and quercetin) in RPGLD increased obviously compared with PGLD. These results shed new light on the antidiabetic potential and mechanism of PGL, as well as the "higher efficacy" of the rice-fried processing method in traditional Chinese medicine.