Evaluation on Antidiabetic Properties of Medicinal Plants from Myanmar

Diabetes-Related Mechanisms of Action Involved in the Therapeutic Effect of Croton Species: A Systematic Review

Over the years, ethnopharmacological and phytochemical investigations have been conducted to understand the potential effects of the Croton genus on several diseases. It has been revealed that these terpenoid-rich species traditionally used to treat gastrointestinal diseases, heal wounds, and relieve pain have a wide range of therapeutic effects; however, those used to treat diabetes, as well as their action mechanisms, have not been reviewed so far. Therefore, the main objective of this review was to compile all Croton species that have shown pharmacological effects against diabetes and describe their action mechanisms. Through a search of the literature, 17 species with hypoglycemic, antihyperglycemic, antilipidemic, antihypertensive, antioxidant, and anti-inflammatory effects were found. Among the mechanisms by which they exerted these effects were the inhibition of α-glucosidases, the promotion of insulin secretion, and the increase in glucose uptake. Interestingly, it was found that some of them may have antihyperglycemic properties, although there were no ethnopharmacological reports that support their traditional use. Moreover, others only presented studies on their hypoglycemic effect in fasting, so further works are encouraged to describe the mechanisms involved in lowering fasting blood glucose levels, such as hepatic glucose production, especially for C. cajucara, C. cuneatus, C. gratissimus var. gratissimus, C. guatemalensis, and C. membranaceus. It is expected that this review contributes to the plant science knowledge of the genus, and it can be used in future references on the identification and development of new molecules/phytomedicines that help in the treatment of diabetes.

Inhibitory effect of Mexican oregano (Lippia graveolens Kunth) extracts on digestive enzymes in vitro, and beneficial impact on carbohydrates and lipids absorption in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Although Mexican oregano inhibits digestive enzymes in vitro its effect on the absorption of carbohydrates and lipids in vivo has not been addressed.

AIM OF THE STUDY

Assess the effect of Mexican oregano (Lippia graveolens Kunth) on carbohydrates and lipids absorption in vivo. The antioxidant activity also was investigated.

MATERIALS AND METHODS

Enzymatic inhibitory action of lipase, α-amylase, and α-glucosidase was evaluated in vitro. Oral lipid (OLTT) and starch tolerance tests (OSTT) were conducted with L. graveolens acetone (O-A) and ethanol (O-E) extracts (at 102 mg/kg body weight equivalent to a 1 g human doses) in male Wistar rats. The antioxidant activity was evaluated through inhibition of lipid peroxidation and scavenging radical.

RESULTS

Both extracts exhibited higher inhibitory median concentration (IC₅₀) of lipase activity (1.9 μg/μL for O-E and 1.8 μg/μL for O-A) than the positive control (Orlistat) (0.07 μg/μL). The IC₅₀ of α-amylase was higher (41.8 μg/μL for O-E and 25.2 μg/μL for O-A) than the Acarbose (2.5 μg/μL); while α-glucosidase results showed not statistically differences between groups (∼1.7 μg/μL). The OLTT results showed that both extracts significantly reduced serum triglycerides (∼147 mg/dL for O-E and ∼155 mg/dL for O-A) as compared with negative control group (only lipid load). In the OSTT, glucose levels showed a significant decrease (∼31 mg/dL for O-E and ∼17 mg/dL for O-A) than the negative control group (only starch load). About in vitro antioxidant evaluation, not statistically differences between extracts and positive control (Trolox) were observed for scavenged free radicals (∼2.0 μg/μL); whereas O-A inhibited lipid peroxidation similar to the Trolox (∼0.8 μg/μL IC₅₀). The main chemical composition of both extracts was coumaric acid, luteolin, rutinoside, naringenin, and carvacrol.

CONCLUSIONS

Both extracts reduce lipid absorption; whereas O-E decreases carbohydrate absorption in vivo. Both extracts inhibit lipid peroxidation and scavenging free radicals in vitro.

In Vitro Evaluation of Cytotoxic Potential of Caladium lindenii Extracts on Human Hepatocarcinoma HepG2 and Normal HEK293T Cell Lines

Data regarding the therapeutic potential of Caladium lindenii (C. lindenii) are insufficient. It becomes more important to explore plants as an alternative or palliative therapeutics in deadly diseases around the globe. The current study was planned to explore C. lindenii for its anticancer activity of ethanolic and hexane extracts of C. lindenii leaves against hepatic carcinoma (HepG2) and human embryonic kidney (HEK293T) cell lines. HepG2 and HEK293T cells were treated with 10, 50, 100, 200, and 400 μg/mL of ethanolic and hexane extracts of C. lindenii and were incubated for 72 h. Antiproliferative activity was measured by 3-(4,5-dimethylthiazol-2yl)-2,5-biphenyl tetrazolium bromide (MTT) assay, and percentage viability were calculated through crystal violet staining and cellular morphology by Floid Cell Imaging Station. The study showed ethanolic extract exhibiting a significantly higher antiproliferative effect on HepG2 (IC50 = 31μg/mL) in a concentration-dependent manner, while HEK293T (IC50 = 241μg/mL) cells showed no toxicity. Hexane extract exhibited lower cytotoxicity (IC50 = 150μg/mL) on HepG2 cells with no effect on HEK293T (IC50 = 550μg/mL). On the other hand, the percentage viability of HepG2 cells was recorded as 78%, 67%, 50%, 37%, and 28% by ethanolic extracts, and 88%, 80%, 69%, 59%, and 50% by hexane extracts at tested concentrations of both extracts. Toxicity assay showed significantly safer ranges of percentage viabilities in normal cells (HEK293T), i.e., 95%, 90%, 88%, 76%, and 61% with ethanolic extract and 97%, 95%, 88%, 75%, and 62% with hexane extract. The assay validity revealed 100% viability in the control negative (dimethyl sulfoxide treated) and less than 45% in the control positive (cisplatin) on both HepG2 and HEK293T cells. Morphological studies showed alterations in HepG2 cells upon exposure to >50 μg/mL of ethanolic extracts and ≥400 μg/mL of hexane extracts. HEK293T on the other hand did not change its morphology against any of the extracts compared to the aggressive changes on the HepG2 cell line by both extracts and positive control (cisplatin). In conclusion, extracts of C. lindenii are proved to have significant potential for cytotoxicity-induced apoptosis in human cancer HepG2 cells and are less toxic to normal HEK293T cells. Hence C. lindenii extracts are proposed to be used against hepatocellular carcinoma (HCC) after further validations.