Biological and pharmacological activities of root extracts and isolated compounds of Hemannia Geniculata
Adeniran, Lateef Ariyo
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Hermannia geniculata is of the genus of flowering plant from the subfamily Byttnerioideae in the family Malnaceae. H. geniculata has been used in treatment of several diseases like colic, diabetes mellitus and other oxidative stress induced illnesses. The dry root material is chopped, boiled in water and taken three times daily to ameliorate blood sugar disorders, management of diarrhoea, heartburn, stomach disorder and flatulency called “leletha” in pregnant Basotho women. Phytochemical analysis revealed the presence of saponin, phenols, flavonoids, alkaloids, tannin, phytosterol, triterpenes and anthraquinone. Ethanolic extract exhibited the highest free radical scavenging capability with the lowest IC50 value (0.52, 0.38, 0.59, 0.63, 0.39 mg/mL) for 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2-Azino-bis(3-ethylbenzothiazoline-6-Sulphonic acid (ABTS), hydroxyl radical, superoxide anion radical, metal chelating ability which is significantly lower (p<0.05) than the standard silymarin while hydro-ethanol has the highest reducing power showing a significant (p<0.05) IC50 value of 0.24 mg/mL compared to citrate (IC50 value; 0.5 mg/mL). In antidiabetic studies, ethanolic extract was a potent inhibitor of α-glucosidase (IC50; 0.01 mg/mL) which is significantly lower (p<0.05) than standard acarbose IC50 value (0.52 mg/mL) and hydro-ethanol decoction and aqueous extracts. It also has a milder percentage inhibition of α-amylase enzyme with IC50 (0.57mg /mL) which is significantly higher (p<0.05) than the standard acarbose IC50 (0.047 mg/mL). The mode of inhibition of α-amylase is by competitive inhibition and uncompetitive inhibition of the α-glucosidase enzyme was observed in ethanolic extract. These findings provide an empirical rationalization for the use of the root extract of Hermannia geniculata in the management of diabetes mellitus and other oxidative stress induced ailments. The Vero, HepG2 and RAW 264.7 macrophage cell lines were used to determine the toxicity of the extracts on cells. Similarly, the capabilities of the extract to inhibit 5-lipoxygenase enzyme activities and overproduction of nitric oxide from LPS-activated RAW 264.7 macrophages were evaluated. Results showed selective toxicity of the extracts with LC50 values of Vero cells ranges from (0.40-0.57 mg/mL) while the LC50 value of HepG2 cells varies from (0.016-0.136 mg/mL). The selectivity index (SI) were (31.87, 18.87, 33.33 and 3.52) for ethanol, hydro-ethanol, decoction and aqueous extracts respectively. The ethanolic extract inhibited NO production in a concentration dependent manner. There was a decrease of 82% at concentration of 0.1 mg/mL and the LC50:3.64 mg/mL is lower and significantly different (p<0.05) compared to the reference compound quercetin with LC50 value of 8.28 mg/mL. Similarly, the ethanolic extract exhibited potent inhibition of 5-lipoxygenase enzyme with the lowest IC50 value of 0.14 mg/mL which is significantly different (p<0.05) compared to all other extracts and indomethacin. The GCMS chromatograms revealed five compound (2-keto-butyric-acid, 2, 2-Bis (4-nitrobenzyl)-1-phenylbutane-1,3-dione, n-Undecane, 1,4,5,8-tetrathiadelin and imidazo-1,5-pyrimidine) which has been reported to have antioxidant, anti-inflammatory and antifungal properties. This result suggested that Hermannia geniculata roots extract is not toxic and possesses antioxidant, antinflammatory and anticancer activities which could be exploited in development of new safe and effective drugs. The chemical profiling and in vitro biological activities of flavonoids of Hermannia geniculata (FHG) roots was also investigated using High Pressure Thin Layer Chromatography (HPTLC) finger print analysis. Antioxidant, antidiabetic anti-inflammatory activities and the ability of FHG extract to inhibit the production of nitric oxide (NO) in lipopolysaccharide (LPS) activated RAW264.7 Macrophage were investigated using standard methods. The selective cytotoxicity of the extract on Vero and HepG2 cells was also determined. Kaempferol (Rf 0.81) was detected in the extract, its Rf value is similar and comparable with the kaempferol standard used (Rf 0.80). Other flavonoids were also present in the extracts with their Rf values of 0.08-0.95. The FHG extract showed commendable antioxidant properties with IC50 values (3.07± 0.12, 2.13± 0.67) for DPPH and ABTS radicals which was lower and significantly different (p<0.05) compared to standard silymarin with IC50: (3.55± 0.10, 2.77± 0.75) for DPPH and ABTS respectively. The results indicated milder inhibition of α-amylase with IC50: (5.55± 0.37) which was higher and significantly different from the standard acarbose with IC50: (3.81± 0.29) Nevertheless, the extract exhibited 73% inhibition of α-glucosidase which exerted better inhibitory effect on 5-lipoxygenase enzyme than indomethacin with their respective IC50: (10.15± 0.02 and 12.03± 0.02). Inhibition of NO production was observed in LPS activated RAW 264.7 Macrophages with the highest concentration of 0.1 mg/mL decreasing NO production by 87%. Selective toxicity of Vero and HepG2 cells with their respective LC50 value of (>1 and 0.02 mg/mL) was also observed. The antiproliferative potentials of the extract was confirmed with Selectivity Index of 50. This study indicated for the first time that FHG extract was non-toxic to normal cells and possess antioxidant, antidiabetic, anti-inflammatory and antiproliferative activities. The bioactive constituent and pharmacological activities of phenols extracted from Hermannia geniculata (PoHG) roots was investigated using in vitro methods. The chemical profile was determined by HPTLC analysis. Antioxidant, antidiabetic, anti-inflammatory and cytotoxic effect of PoHG on Vero and HepG2 cells was carried out using standard procedures. Phenolic compounds were detected in the sample at Rf (0.14, 0.81 and 0.95). PoHG radical scavenging capabilities on DPPH, ABTS+ and superoxide anion radicals were similar to the standard (silymarin). The IC50 values were DPPH (0.12± 0.00), ABTS (0.13± 0.01) and superoxide anion (0.20± 0.00). The values of the metal chelating activity of PoHG extract is lower and significantly different from the standard (silymarin) their respective IC50 values were (0.06± 0.00 and 0.18± 0.01). The antidiabetic effect was determined by its ability to mildly inhibit α-amylase and strongly inhibit α-glucosidase enzymes, the respective IC50 values obtained were (7.52± 0.23 and 1.76 ± 0.14). PoHG extract exhibited a commendable inhibition of 5-lipoxygenase enzyme with IC50 value of (0.15 ± 0.03) which is similar to the IC50: (011 ± 0.01) value for the standard (indomethacin). However, the extract was non-toxic to Vero cells with LC50 value of >1.00 mg/mL but highly toxic to HepG2 cells with LC50: 0.08 mg/mL. The selectivity index of 12.50 was recorded. The presence of phenolics/ carboxylic acids were also confirmed in the extract, the result of the antioxidant, antidiabetic and antinflammatory activities of PoHG suggested that the phenols extract may be useful in the management of oxidative stress induce diseases, type 2 diabetes mellitus and asthma. It is also safe for use and its antiproliferative activities can be exploited in search for anticancer agents. A new xanthene derivative Hermannol (9-(7-methyloctyl)-9H- xanthene-2,3-diol) was isolated from the roots of Hermannia geniculata . The structure was elucidated by analysis of their 1D, 2D NMR, MS and IR spectroscopic data. The compound displayed good antioxidant and antidiabetic activities. In conclusion, it is evident from the study that different crude extracts of H. geniculata roots and its bioactive constituents (flavonoids and phenols), the isolated compound (Hermannol) is non- toxic and possess varied degree of antioxidant, antidiabetic, antiiflammatory and antiproliferative activities which can be exploited for new drug development.