Parmotrema tinctorum exhibits antioxidant, antiglycation and inhibitory activities against aldose reductase and carbohydrate digestive enzymes: an in vitro study

Tinctorin, a new spiroterpenoid from the lichen Parmotrema tinctorum (Despr. ex Nyl.) Hale growing in Vietnam

A new spiroterpenoid, namely tinctorin (1), along with one known compound, norreticulatin (2), were isolated from the lichen Parmotrema tinctorum (Despr. ex Nyl.) Hale. Their structures were elucidated by extensive spectroscopic analyses and electronic circular dichroism (ECD) calculations. The absolute configuration of 2 was established for the first time. Compound 1 was evaluated for its inhibitory activity against α-glucosidase and found to be inactive.

Nutritional and Health-Promoting Effects of Lichens Used in Food Applications

PURPOSE OF REVIEW

Lichens have a huge significance which is used in nutrition due to the bioactive components within. Lichen is a nutrient-dense resourceful diet nearly every day meal and has long been used as food; also, these valuable natural resources are now being utilized for a wide range of other purposes. The purpose of this review was to evaluate the nutritional and edible qualities of lichens as well as the possible health benefits of lichens. It is interesting to note that lichen is a nutrient-dense and functional food. It is a nutritional resource that can mitigate the effects of malnutrition to some amount.

RECENT FINDINGS

There is an indication that an intake of lichens as natural foods was associated with nutritional and health-promoting properties. Lichens have proven to have theoretically rich nutritional value, and their extracts and active constituents have also been shown to have multiple health benefits. Low-fat content, high carbohydrate, and crude fibre content; plentiful mineral components; and good protein sources are all thought to contribute to lichen's nutritional value. There is a lot of potential for using lichens as an effective food source and ensuring people's food production.

Tinctoride A, a New Hopan-Type Triterpenoic Peracid from the Thallus of Lichen Parmotrema Tinctorum (Despr. ex Nyl.) Hale

A new hopan-type triterpenoic peracid, tinctoride A (1), together with three known compounds, zeorin (2), 6β,22-dihydroxyhopane (3), and ergosterol peroxide (4), was isolated from Parmotrema tinctorum (Despr. ex Nyl.) Hale. Their chemical structures were identified by extensive 1D and 2D NMR analysis and high-resolution mass spectroscopy and compared with those reported in the literature. The enzyme inhibitory potential of compounds 1–3 against α-glucosidase was investigated, exhibiting nil to weak inhibitory activity.

Potential of Usnic Acid Compound from Lichen Genus Usnea sp. as Antidiabetic Agents

Lichen Usnea sp. is potential as a new natural medicine. This study report isolation of secondary metabolites from lichen Usnea sp. and α-glucosidase inhibitory, which is potential as an antidiabetic agent. Lichen powder was macerated using methanol, separated using column chromatography gravity and thin-layer chromatography. The crystalline was isolated and purified by the recrystallization process for obtaining pure compound. The isolated compound was determined using FTIR and NMR spectroscopy (¹H and ¹³C). The results showed that the isolated compound was yellow needle crystals. Based on the spectra data interpretation, it was obtained usnic acid compound with the molecular formula of C₁₈H₁₆O₇. The α-glucosidase inhibitory activity test showed that the usnic acid had activity in inhibiting the α-glucosidase enzyme with an IC₅₀ value of 106.78 µg/mL. The usnic acid from Usnea sp. has a very good impact on the source of natural compounds as an antidiabetic drug in the future.

In silico analysis of a potential antidiabetic phytochemical erythrin against therapeutic targets of diabetes

Diabetes mellitus is a multifactorial disorder characterized by a chronic elevation in blood glucose levels. Currently, antidiabetic drugs are available to counteract the associated pathologies. Their concomitant effects necessitate the investigation for an effective and safe drug aimed to diminish blood glucose levels with fewer side effects. Several researchers are taking new initiatives to explore plant sources as they are known to contain a wide variety of active agents. Hence, the present study was undertaken to study the role of natural products using in silico interaction studies. Erythrin a compound present in lichens was selected as a potential anti-diabetic agent. Molecular docking studies were carried out with 14 target proteins to evaluate its antidiabetic potential. Molecular docking analysis resulted in favourable binding energy of interaction ranging as low as - 119.676 to - 92.9545 kcal/mol for erythrin, Analogue showed the highest interactions with 3C45 (- 119.676 kcal/mol) followed by 2Q5S (- 118.398 kcal/mol), 1XU7 (- 117.341 kcal/mol), 3K35 (- 114.267 kcal/mol). Erythrin was found to fare better than the three clinically used antidiabetic compounds, metformin, repaglinide and sitagliptin. Further, the molecular interactions between erythrin and the diabetes related target proteins was established by analysing the interactions with associated amino acids. In silico pharmacokinetics and toxicity profile of erythrin using admetSAR software predicted erythrin as non-carcinogenic and non-mutagenic. The drug-likeliness was calculated using molsoft software respecting Lipinski's rule of five. The compound was found to comply with Lipinksi rules violating only one filter criterion. The study suggested that erythrin could be a potential anti-diabetic agent.

Two new phenolic compounds from the Vietnamese lichen Parmotrema tinctorum

Chemical investigation of the lichen Parmotrema tinctorum (Nyl.) Hale led to the isolation of two new phenolic compounds, 2-ethylhexyl orsellinate (1) and tinctorinone (2). The structures were determined by analysis of their MS and NMR data as well as by comparison with literature data. The 2-ethylhexyl ester group of 2-ethylhexyl orsellinate is uncommon among lichen metabolites. Tinctorinone revealed strong inhibition towards α-glucosidase.

Potential of Lichen Compounds as Antidiabetic Agents with Antioxidative Properties: A Review

The advancement in the knowledge of potent antioxidants has uncovered the way for greater insight in the treatment of diabetic complications. Lichens are a rich resource of novel bioactive compounds and their antioxidant potential is well documented. Herein we review the antidiabetic potential of lichens which have received considerable attention, in the recent past. We have correlated the antidiabetic and the antioxidant potential of lichen compounds. The study shows a good accordance between antioxidant and antidiabetic activity of lichens and points out the need to look into gathering the scarce and scattered data on biological activities for effective utilization. The review establishes that the lichen extracts, especially of Parmotrema sp. and Ramalina sp. have shown promising potential in both antidiabetic and antioxidant assays. Ubiquitous compounds, namely, zeorin, methylorsellinate, methyl-β-orcinol carboxylate, methyl haematommate, lecanoric acid, salazinic acid, sekikaic acid, usnic acid, gyrophoric acid, and lobaric acid have shown promising potential in both antidiabetic as well as antioxidant assays highlighting their potential for effective treatment of diabetic mellitus and its associated complications. The available compilation of this data provides the future perspectives and highlight the need for further studies of this potent herbal source to harvest more beneficial therapeutic antidiabetic drugs.

Characterization of Emodin as a Therapeutic Agent for Diabetic Cataract

Aldose reductase (AR) in the lens plays an important role in the pathogenesis of diabetic cataract (DC) by contributing to osmotic and oxidative stress associated with accelerated glucose metabolism through the polyol pathway. Therefore, inhibition of AR in the lens may hold the key to prevent DC formation. Emodin, a bioactive compound isolated from plants, has been implicated as a therapy for diabetes. However, its inhibitory activity against AR remains unclear. Our results showed that emodin has good selectively inhibitory activity against AR (IC50 = 2.69 ± 0.90 μM) but not other aldo-keto reductases and is stable at 37 °C for at least 7 days. Enzyme kinetic studies demonstrated an uncompetitive inhibition against AR with a corresponding inhibition constant of 2.113 ± 0.095 μM. In in vivo studies, oral administration of emodin reduced the incidence and severity of morphological markers of cataract in lenses of AR transgenic mice. Computational modeling of the AR-NADP(+)-emodin ternary complex indicated that the 3-hydroxy group of emodin plays an essential role by interacting with Ser302 through hydrogen bonding in the specificity pocket of AR. All the findings above provide encouraging evidence for emodin as a potential therapeutic agent to prevent cataract in diabetic patients.