Antioxidant Activity andα-Amylase Inhibitory Effect of Polyphenolic-Rich Extract fromOriganum GlandulosumDesf

Oregano as a potential source of antidiabetic agents

Oregano is the name given to a great variety of herbs belonging mainly to the Lamiaceae and Verbenaceae botanical families. Oregano species are rich sources of phytochemicals such as phenolic compounds like rosmarinic acid, salvianolic acid, and luteolin, among others. A few articles have previously accessed some potential pharmacological bioactivities of oregano plants; however, none has focused on the antidiabetic studies. This review aims to summarize recent studies about the potential effect of phenolic compounds from oregano plant species. The reports were retrieved from electronic databases such as PubMed, Web of Science, National Center for Biotechnology Information (NCBI), and Scopus. In addition, articles related to the mentioned topics and published between 2004-2022 were selected. The results from this study show that the antidiabetic pharmacological reports of oregano phenolic compounds are mainly in vitro reports. Therefore, the diversity of oregano species yields a broad variety of phenolic constituents, where preclinical and clinical studies are strongly recommended.

Efficacy of Rytigynia senegalensis Blume on Free Radical Scavenging, Inhibition of α-Amylase and α-Glucosidase Activity, and Blood Glucose Level

Rytigynia senegalensis (Rubiaceae) is a plant used in African medicine for the treatment of diabetes. The aim of this study was to evaluate the in vitro antioxidant, enzyme inhibitory, and hypoglycemic effects of Rytigynia senegalensis extract (RSE). The contents of phenols, tannins, and flavonoids were determined by phytochemical screening. 2,2-Azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 2,2-diphenylpicrylhydrazyl (DPPH) were determined to evaluate the free radical scavenging capacity of the RSE. The inhibitory activity of α-amylase and α-glucosidase was evaluated in vitro using the α-amylase and α-glucosidase inhibition methods and in vivo using the sucrose and starch tolerance tests. The glucose tolerance test was performed on normal rats using doses of 50, 100, and 200 mg/kg of RSE. RSE contains total phenols (36.35 mg GAE/g of extract), flavonoids (11.91 mg QE/g of extract), and tannins (13.01 mg CE/g of extract). RSE exhibits significant radical scavenging activity on DPPH and ABTS radicals with an IC₅₀ of 17.51 and 21.89 μg/mL, respectively. RSE showed an inhibitory effect on the activity of α-amylase and α-glucosidase with an IC₅₀ of 308.93 and 354.13 μg/mL, respectively. RSE (100 and 200 mg/kg) caused a significant decrease in area under the curve and postprandial glycemia at 60, 90, and 120 min following the administration of starch or sucrose. Regarding the glucose tolerance test, RSE (100 and 200 mg/kg) significantly reduced postprandial hyperglycemia from the 90th min posttreatment. RSE lowered postprandial hyperglycemia and has antioxidant properties. These effects would be due to the presence of bioactive compounds in the RSE.

Understanding glycaemic control and current approaches for screening antidiabetic natural products from evidence-based medicinal plants

Type 2 Diabetes Mellitus has reached epidemic proportions as a result of over-nutrition and increasingly sedentary lifestyles. Current therapies, although effective, are not without limitations. These limitations, the alarming increase in the prevalence of diabetes, and the soaring cost of managing diabetes and its complications underscores an urgent need for safer, more efficient and affordable alternative treatments. Over 1200 plant species are reported in ethnomedicine for treating diabetes and these represents an important and promising source for the identification of novel antidiabetic compounds. Evaluating medicinal plants for desirable bioactivity goes hand-in-hand with methods in analytical biochemistry for separating and identifying lead compounds. This review aims to provide a comprehensive summary of current methods used in antidiabetic plant research to form a useful resource for researchers beginning in the field. The review summarises the current understanding of blood glucose regulation and the general mechanisms of action of current antidiabetic medications, and combines knowledge on common experimental approaches for screening plant extracts for antidiabetic activity and currently available analytical methods and technologies for the separation and identification of bioactive natural products. Common in vivo animal models, in vitro models, in silico methods and biochemical assays used for testing the antidiabetic effects of plants are discussed with a particular emphasis on in vitro methods such as cell-based bioassays for screening insulin secretagogues and insulinomimetics. Enzyme inhibition assays and molecular docking are also highlighted. The role of metabolomics, metabolite profiling, and dereplication of data for the high-throughput discovery of novel antidiabetic agents is reviewed. Finally, this review also summarises sample preparation techniques such as liquid-liquid extraction, solid phase extraction, and supercritical fluid extraction, and the critical function of nuclear magnetic resonance and high resolution liquid chromatography-mass spectrometry for the dereplication, putative identification and structure elucidation of natural compounds from evidence-based medicinal plants.

Flavonoids and Phenolic Acids from Oregano: Occurrence, Biological Activity and Health Benefits

Several herb species classified as oregano have been widely used in folk medicine to alleviate inflammation-related diseases, respiratory and digestive disorders, headaches, rheumatism, diabetes and others. These potential health benefits are partially attributed to the phytochemical compounds in oregano such as flavonoids (FL) and phenolic acids (PA). Flavonoids and phenolic acids are among the most abundant and most studied phytochemicals in oregano species. Epidemiological, in vitro and in vivo experiments have related long-term consumption of dietary FL and PA with a decreased risk of incidence of chronic diseases. The aim of this manuscript is to summarize the latest studies on the identification and distribution of flavonoids and phenolic compounds from oregano species and their potential antioxidant, anti-inflammatory and anti-cancer health benefits.