Antioxidant and Inhibitory Effects of Saponin Extracts from Dianthus basuticus Burtt Davy on Key Enzymes Implicated in Type 2 Diabetes In vitro

CONTEXT: Dianthus basuticus is a plant of South African origin with various acclaimed pharmaceutical potentials. AIMS: This study explored the antioxidant and antidiabetic activities of saponin extract from D. basuticus in vitro. MATERIALS AND METHODS: Antioxidant activity of saponin was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (*NO)-free radical scavenging activity while antidiabetic potentials were measured by the α-amylase and α-glucosidase inhibitory activities of the saponin extract. RESULTS: The results showed that the saponin extract, compared with quercetin, displayed better DPPH (IC(50) = 6.95 mg/ml) and NO (IC(50) = 3.31 mg/ml) radical scavenging capabilities. Similarly, the saponin extracts elicited stronger α-glucosidase (IC(50) = 3.80 mg/ml) and moderate α-amylase (IC(50) = 4.18 mg/ml) inhibitory activities as compared to acarbose. Saponin exhibited a competitive mode of inhibition on α-amylase with same maximum velocity (Vmax) of 0.0093 mM/min for saponin compared with control 0.0095 mM/min and different the Michaelis constant (Km) values of 2.6 × 10(-6) mM and 2.1 × 10(-5) mM, respectively, while for α-glucosidase, the inhibition was uncompetitive, Vmax of 0.027 mM/min compared with control 0.039 mM/min and Km values of 1.02 × 10(-6) mM and 1.38 × 10(-6) mM, respectively. The gas chromatography-mass spectrometric analysis revealed the presence of bioactive like β- and α-amyrin, 3-O-methyl-D-glucose, methyl commate, and olean-12-en-3-beta-ol. CONCLUSION: Overall, the data suggested that the saponin extract from D. basuticus has potentials as natural antioxidants and antidiabetics. SUMMARY: Saponin extract from Dianthus basuticus displayed promising antidiabetic and antioxidant activity. Saponin competitively and uncompetitively inhibited a-amylase and a-glucosidase, respectively. The stronger inhibition of α-glucosidase and moderate inhibition of α-amylase by saponin extract from D. basuticus is promising good antidiabetes compared with existing drugs with associated side effects. [Image: see text] Abbreviations used: DPPH: 2,2-diphenyl-1-picrylhydrazyl, Km: The Michaelis constant, Vmax: Maximum velocity, ROS: Reactive oxygen species, NIDDM: Non-insulin-dependent diabetes mellitus, UFS: University of the Free State, GC-MS: Gas chromatography-mass spectrometric, MS: Mass spectrometry, NIST: National Institute of Standards and Technology, DNS: 3,5-dinitrosalicylic acid, NO: Nitric oxide, RNS: Reactive nitrogen species, PNPG: p-Nitrophenyl-α-D-glucopyranoside.