Nelumbo nucifera Gaertn., a perennial aquatic plant, which was distributed throughout Asia, including India, China, the Middle east and Egypt. In particular, the rhizomes of N. nucifera, have been used foodstuffs as well as traditional medicines in Ch...
Nelumbo nucifera Gaertn., a perennial aquatic plant, which was distributed throughout Asia, including India, China, the Middle east and Egypt. In particular, the rhizomes of N. nucifera, have been used foodstuffs as well as traditional medicines in China, India and Korea. Various pharmacological activities of the N. nucifera rhizomes, including antimicrobial, antioxidant, antiobese, antidiabetic, anti-Alzheimer, and antihypertensive effects have been reported. However, the diabetic complications effect of the rhizomes is unclear, and its antidiabetic and antioxidant effects is yet limited. Therefore, the preventive and therapeutic potency against oxidative stress and diabetic complications of Nelumbo nucifera were evaluated via the 1,1-diphenyl-2-picrylhydrazyl (DPPH), total reactive oxygen species (ROS) assays, as well as the rat lens aldose reductase (RLAR) and the human recombinant aldose reductase (HRAR) assays. In addition, the anti-diabetic effect of the rhizomes was determined via the protein tyrosin Protein tyrosine phosphatase (PTP) 1B assay.
The MeOH extract of the N. nucifera rhizome exhibited marignal antioxidant effects, however the EtOAc fraction exerted significant antioxidant effects with IC_(50) values of 3.21 and 11.06 μg/ml, by compared with respective positive controls, L-ascorbic acid (IC_(50) 5.16 μg/ml) and trolox (IC_(50) 5.19 μg/ml) in the DPPH and total ROS assays, respectively. Also, the N. nucifera rhizome showed remarkable RLAR inhibitory effects with IC_(50) values of 7.70 μg/ml, by compared with positive control, quercetin (IC_(50) 3.28 μg/ml), however, no HRAR inhibitory effects within test concentration (f.c. 50 μg/ml). Interetingly, the EtOAc and n-BuOH fractions exerted predominant inhibitory effects with respective IC_(50) values of 0.15 and 0.68 μg/ml in the RLAR assay; 10.76 and 33.95 μg/ml in the HRAR assay. In the PTP1B assay, the CH₂Cl₂ fraction, along with the AR inhibitory EtOAc and n-BuOH fractions appeared significant inhibitory effects with IC_(50) values of 4.09, 0.85, and 6.76 μg/ml, by compared with a positive control, ursolic acid (IC_(50) 1.80 μg/ml). Since tryptophan was previously isolated to be antidiabetic components, the PTP1B inhibitory effect of this compound was evaluated in this study. This component showed great PTP1B inhibitory effect with an IC_(50) value of 4.75 μg/ml.
In conclusion, the above results suggest that the rhizomes of of N. nucifera, and tryptophan contained within them, would clearly have potential uses in the development of therapeutic or preventive agents for oxidative stress, diabetic complications, and diabetes.