Antarvedisides A-B from Manglicolous Lichen Dirinaria consimilis (Stirton) and their Pharmacological Profile

Beneficial Effects of Liposomal Formulations of Lichen Substances: A Review

Lichens are commonly used as essential traditional medicines to treat various conditions, including skin disorders, wounds, digestive, respiratory, obstetric, and gynecological problems in many cultures in Africa, Asia, Europe, Haitian, Oceania, and North and South America. Lichens have been deeply investigated for their phytochemical properties, and to date, numerous compounds (also known as substances) have been successfully isolated from the extracts. However, the low solubility and bioavailability of pure lichen substances have been widely recognized as the significant issues hindering their biological applications. Recently, several groups have investigated the properties and the potential applications of lichen metabolites-based liposomal formulations and revealed a substantial improvement in their solubility, bioactivity, and toxicity in the animal. Thus, in this topical review, we aimed to provide an overview of liposomal structures, the efficacy of liposomal formulations, as well as their beneficial effects as compared to the free compounds themselves.

In vitro antimycobacterial studies of flavonols from Bauhinia vahlii Wight and Arn

Mycobacterial infections and fast-growing strains are increasing globally with 8 million new cases and 1.8 million fatalities per annum worldwide. The acid-fast bacterium, Mycobacterium tuberculosis (M.t), can spread diseases like tuberculosis (Tb) and weaken the immune system. In Ayurveda, the Bauhinia genus is most valued for the treatment of tuberculosis lymphadenitis. The objective of the present study is to identify anti-tubercular compounds from the under-investigated medicinal plant B. vahlii Wight and Arn. using bioassay guided isolation. The antimycobacterial activity was evaluated against non-virulent strains: Mycobacterium tuberculosis H37Ra (ATCC 25177) and Mycobacterium bovis BCG (ATCC 35743). Also, antibacterial and cytotoxicity activities were tested to identify the specificity of the isolated metabolites. Bioassay-guided isolation yielded three known flavonols, namely quercetin (1), ombuin (2), and kaempferol (3), from the methanolic extract of bark of B. vahlii. The results of antimycobacterial activity tests revealed that 2 showed much better mycobactericidal activity than 1 and 3 under ex vivo condition with minimum inhibitory concentration (MIC) values ranged from 0.05 ± 0.01 to 0.26 ± 0.01 nM, and half-maximal inhibitory concentration (IC₅₀) values ranged from 2.85 ± 0.14 to 7.21 ± 1.09 nM against dormant and active forms, respectively. Also, compound 2 showed higher resistance with MIC values > 100 μg/mL against both Gram-positive and Gram-negative bacteria and the least cytotoxicity up to 100 μg/mL concentration against the tested series of cancer cell lines. The results revealed the Ayurvedic use of extracts of the Bauhinia genus for treating tuberculosis, and the key bioactive compounds were found to be flavonols (1–3). The present work provides the first evidence for the presence of antimycobacterial compounds in B. vahlii.

Evaluating the In Vitro Activity of Depsidones from Usnea subfloridana Stirton as Key Enzymes Involved in Inflammation and Gout

Background: Traditionally, Usnea genus has significant uses in the treatment of swelling and tumors in Africa and Asia. The aim of the present study was to investigate the chemical constituents present in the acetone extract (AE) of Usnea subfloridana Stirton and also to evaluate their anti-inflammatory and anti-gout effects. Methods: Isolation and characterization of secondary metabolites from AE were evaluated by chromatography and spectral studies. Anti-inflammatory activities were assessed through cyclooxygenase (COX1 and COX2) and 5-lipooxygenase (5-LOX) enzyme inhibition assays, while anti-gout effects were evaluated by xanthine oxidase (XO) inhibition assay. Results: The existence of five known depsidones, identified as galbinic acid (1), conprotocetraricacid (2), constictic acid (3), salazinic acid (4), and lobaric acid (5), were exposed by chemical investigation of AE and confirmed by spectral data. Using in vitro enzyme inhibition assays, it was noticed that all the isolates showed dose-dependent activity against all the tested enzymes. Mainly, compounds 2 and 5 showed better inhibition efficiency on COX2 enzyme with the IC50of 7.17±1.07 and 7.01±0.94 nM, respectively, than the reference drug indomethacin (7.3±0.65nM). Furthermore, all isolates exhibited potent inhibition effects on the XO enzyme. Conclusion: The results indicated that U. subfloridana can be a favorable natural source for thetreatment of inflammation and gout. Compounds 2 and 5 were responsible for these biologicalactions by regulating pro-inflammatory enzymes, namely COXs, 5-LOX, and XO.

Sekikaic acid modulates pancreatic β-cells in streptozotocin-induced type 2 diabetic rats by inhibiting digestive enzymes

The antioxidant and antidiabetic effects of sekikaic acid (SA) were investigated using in vitro and in vivo study models. SA possessed good antioxidant activity as assessed through hydroxyl radicals (IC₅₀ value = 41.5 µg/mL) and ferric ions assay (IC₅₀ value = 42.0 µg/mL). SA exhibited stronger α-glucosidase and α-amylase inhibition than that of aldose-reductase and protein tyrosine phosphatase 1B. The hypoglycemic activity of SA caused significant reduction of plasma glucose levels in normal and glucose loaded rats. The anti-hyperglycemic activity of SA (2 mg/Kg body weight) was indicated by the reduction of blood glucose by 44.17 ± 3.78% in the third week in streptozotocin-induced diabetic rats. The hypolipidaemic action of SA was evident by the significant decrease in the levels of low-density lipoprotein, total cholesterol, and total glycerides. Histologically, the pancreas of the treated groups showed significant regeneration of the pancreatic β-cells compared to diabetic control, possibly due to the inhibition of digestive enzymes.

Protective effects of extracts of lichen Dirinaria consimilis (Stirton) D.D. Awasthi in bifenthrin- and diazinon-induced oxidative stress in rat erythrocytes in vitro

The intoxication of insecticides such as bifenthrin and diazinon has been reported to generate free radicals, and thereby alter the antioxidant defense system in erythrocytes. The present study is aimed to investigate the protective effects of acetone (DA) and methanolic (DM) extracts of lichen Dirinaria consimilis against bifenthrin and diazinon toxicity in rats' erythrocytes in vitro. Rats' erythrocytes were exposed to bifenthrin and diazinon, individually and also in combination with DA or DM at 1 ppm for 3 h at 37 ˚C. By using spectrophotometric methods, all the samples were estimated for changes in hemoglobin (Hb) concentration, malondialdehyde (MDA) levels, and enzyme [Superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferases (GST)] activities. The outcomes showed that both the insecticides were highly toxic to rats' erythrocytes. Among all groups, both the insecticides and DA exposed groups showed very low levels of MDA content, and GST activity in rats' erythrocytes, when compared to the control. Besides, DA groups pretreated with both insecticides showed significant improvement of total Hb concentration, SOD, and CAT activities, with respect to the control. Hence, the present results indicate that the extracts of D. consimilis act as an antioxidant agent that reduces oxidative stress burden in insecticides toxicity.

Anticancer Potential of Lichens' Secondary Metabolites

Lichens produce different classes of phenolic compounds, including anthraquinones, xanthones, dibenzofuranes, depsides and depsidones. Many of them have revealed effective biological activities such as antioxidant, antiviral, antibiotics, antifungal, and anticancer. Although no clinical study has been conducted yet, there are number of in vitro and in vivo studies demonstrating anticancer effects of lichen metabolites. The main goal of our work was to review most recent published papers dealing with anticancer activities of secondary metabolites of lichens and point out to their perspective clinical use in cancer management.