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

Abstract

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 (IC₅₀ = 6.95 mg/ml) and NO (IC₅₀ = 3.31 mg/ml) radical scavenging capabilities. Similarly, the saponin extracts elicited stronger α-glucosidase (IC₅₀ = 3.80 mg/ml) and moderate α-amylase (IC₅₀ = 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 activitySaponin competitively and uncompetitively inhibited a-amylase and a-glucosidase, respectivelyThe 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. 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.

Keywords: Antidiabetics; Dianthus basuticus; antioxidants; saponin.

Figure 1

2,2-diphenyl-1-picrylhydrazyl radical scavenging activity of saponin extract from Dianthus basuticus

Figure 2

Nitric oxide scavenging activity of saponin extract from Dianthus basuticus

Figure 3

α-amylase inhibitory activity of saponin extract from Dianthus basuticus

Figure 4

α-glucosidase inhibitory activity of saponin extract from Dianthus basuticus

Figure 5

Modes of inhibition of α-glucosidase by saponin extract from Dianthus basuticus

Figure 6

Modes of inhibition of α-amylase by saponin extract from Dianthus basuticus

Figure 7

Gas chromatography-mass spectrometric chromatogram of the saponin extract of Dianthus basuticus