Variation in gymnemic acid content and non-destructive harvesting of Gymnema sylvestre (Gudmar)

Antioxidant and Phytochemical Potential of and Phytochemicals in Gymnema inodorum (Lour.) Decne in Northern Thailand

Gymnema inodorum (Lour.) Decne is a vegetable local to Chiang Mai Province of Northern Thailand. This study aimed to analyze the antioxidant and phytochemical potential of G. inodorum found in Chiang Mai Province; antioxidant compounds of G. inodorum were tested via DPPH, ABTS and FRAP assays, and total phenolic compound and total flavonoid contents were analyzed. Anti-inflammatory effects were focused on regarding pharmacological potential. The gymnemic acid level was analyzed by HPLC-UV, and other potential chemicals were analyzed by LC-QTOF/MS. The quantifications of gymnemic acid contents analyzed using HPLC-UV showed that the highest gymnemic acid concentrations were found in the air-dried and roasted 1-day-fermented leaf extracts (0.1258 ± 0.0157 μg/mg). The highest free radical scavenging activity via DPPH assay was found in baked leaf extract, with an IC₅₀ of 8.99 mg/mL, and via ABTS assay in baked and roasted leaf extracts, with an IC₅₀ of 1.05 mg/mL. FRAP assays showed the highest free radical scavenging activity for the baked leaf extract, with 0.0085 ± 0.008 mM Fe²⁺/g sample. The total phenolic contents of fresh G. inodorum leaf extracts obtained with ethanol, methanol and water were 0.19 ± 0.0004, 0.21 ± 0.0010 and 0.10 ± 0.0008 μg GAE/g, respectively. The total flavonoid contents of fresh G. inodorum leaf extracts obtained with ethanol, methanol and water were 74.56 ± 28.00, 71.88 ± 16.11 and 10.74 ± 3.63 μg QE/g, respectively. The LC-QTOF/MS analysis of the fresh G. inodorum leaf extract showed that 6-hydroxykaempferol 7-rutinoside was the most abundant compound. In the study, G. inodorum, a plant local to Northern Thailand, is shown to be a useful plant with high antioxidant and phytochemical potential properties.

Risk assessment of substances used in food supplements: the example of the botanical Gymnema sylvestre

Botanicals and preparations derived from these are among the substances frequently added to foods and food supplements, yet the safety of many botanicals has not been systematically assessed. In the context of the EU‐FORA fellowship programme, the fellow performed an assessment on the safety of the botanical Gymnema sylvestre, in accordance with EFSA's guidance on the assessment of safety of botanicals. Although preparations of G. sylvestre are marketed as food supplements, they may appeal to people who are suffering from metabolic syndrome and/or diabetes mellitus. A scientific literature search was carried out using PubMed/MEDLINE and EMBASE electronic databases. Experience was gained by the fellow in systematic data extraction from scientific publications, structuring of the data and evaluating toxicological key parameters, outcomes of clinical significance, pharmacokinetic and pharmacodynamic interactions, uncertainties and methodological shortcomings of studies. Limited evidence from toxicological in vivo studies and human clinical studies suggested lack of relevant adverse effects of this botanical. However, human studies provided some indications that certain Gymnema extracts may enhance the glucose‐lowering effects of certain antidiabetic drugs. Considering the uncertainties for the composition of different Gymnema preparations, potential herb–drug interactions and the indications of glucose lowering or hypoglycaemic effects, the use of Gymnema‐based food supplements in combination with authorised antidiabetic drugs may be associated with risks. The procedures learned for the safety evaluation of Gymnema may be similarly applied by the fellow for the risk assessment of other substances with nutritional or physiological effect added to foods and food supplements. Furthermore, apart from learning by conducting exercises in risk assessment, the fellow was able to develop other skills (e.g. communication skills), diversify his competencies and expand his network of scientific connections for future collaborations in the field of nutritional risk assessment.

In vivo anti-ulcer, anti-stress, anti-allergic, and functional properties of gymnemic acid isolated from Gymnema sylvestre R Br

BACKGROUND

Gymnema sylvestre is a highly valued ethno pharmacologically important medicinal plant used currently in many poly-herbal formulations due to its potential antidiabetic activity and other health benefits. The present study was carried out to analyze the anti-stress, anti-allergic, and antiulcer activity of the bioactive compounds present in Gymnema sylvestre leaves.

METHODS

The preliminary phytochemical screening for bioactive compounds from aqueous extracts revealed the presence of alkaloids, triterpenes, flavonoids, steroids, and saponins. The antioxidant activities were investigated using DPPH radical scavenging method. The characterization of the extract was carried out using standard compound by High Performance Thin Layer Chromatography (HPTLC) and phytochemical analysis in terms of total phenol, total flavonoids, reducing power and antioxidant potentials, etc. The in vivo studies on albino mice proved the purified fraction has anti-stress/anti-allergic activity against milk induced leucocytosis/eosinophilia and able to inhibit the aspirin induced gastric ulcers.

RESULTS

The quantitative estimation for aqueous extract exhibited total antioxidant (9.13 ± 0.04 μg/g), flavonoids (125.62 ± 26.84 μg/g), tannin (111.53 ± 15.13 μg/g), total phenol content (285.23 ± 1.11 μg/g) and free radical scavenging (52.14 ± 0.32%). Further the aqueous extract was consecutively purified by TLC and silica column chromatography. The purified fractions were characterized by HPTLC and GC-MS and the component was identified as gymnemic acid. The potency of the antimicrobial activity of the extract was studied with bacteria. Pharmacological experiments clearly demonstrated that the extracts of all plants given orally showed significant gastric protection against the asprin-induced gastric ulcer model in mice. Furthermore, healing effects were also confirmed through histopathological examination.

CONCLUSIONS

The aqueous extracts of the leaves of Gymnema sylvestre possess anti ulcerogenic, Anti allergic, Anti stress, properties that may be due to cytoprotective mechanism. These results support the ethno medical uses of the plant in the treatment of gastric ulcer.

The effect of management systems and ecosystem types on bark regeneration in Himatanthus drasticus (Apocynaceae): recommendations for sustainable harvesting

Bark and exudates are widely commercialized non-timber forest products. However, the ecological impacts of the harvesting of these products have seldom been studied. The aim of this study is to investigate the relationship of tree resilience to harvesting intensity in Himatanthus drasticus, a tree that is highly exploited in the Brazilian savanna (Cerrado) for its medicinal latex. Although the traded product is the latex, the traditional harvesting systems involve the removal of the bark of the trees to allow exploitation. A 3-year experiment was conducted in two different Cerrado ecosystems (open savanna and savanna woodland). Trees were debarked at four debarking intensities to simulate the effects of traditional management systems. Measurements of bark growth were taken every 6 months, and quantitative and qualitative indexes of bark regeneration were obtained. The mortality of the debarked trees was low and could not be related to the intensity of harvesting. No signs of attack by fungi or insects were recorded. Compared with other species exploited for bark, H. drasticus is very resilient to harvesting; however, bark regeneration is relatively slow. In both analyzed ecosystems, the regeneration indexes showed higher values in the controls than in the treatments, indicating that 3 years is not sufficient for total recovery of the rhytidome. Bark regeneration occurred primarily by sheet growth and was more rapid in open savanna than in savanna woodland. No differences in the rate of bark recovery were found among management treatments. Based on the results, sustainable harvesting guidelines are suggested for the species.

Sweet-taste-suppressing compounds: current knowledge and perspectives of application

Sweet-tasting compounds are recognized by a heterodimeric receptor composed of the taste receptor, type 1, members 2 (T1R2) and 3 (T1R3) located in the mouth. This receptor is also expressed in the gut where it is involved in intestinal absorption, metabolic regulation, and glucose homeostasis. These metabolic functions make the sweet taste receptor a potential novel therapeutic target for the treatment of obesity and related metabolic dysfunctions such as diabetes. Existing sweet taste inhibitors or blockers that are still in development would constitute promising therapeutic agents. In this review, we will summarize the current knowledge of sweet taste inhibitors, including a sweet-taste-suppressing protein named gurmarin, which is only active on rodent sweet taste receptors but not on that of humans. In addition, their potential applications as therapeutic tools are discussed.