Recent advances on natural depsidones: sources, biosynthesis, structure-activity relationship, and bioactivities

Depsidones are a class of polyphenolic polyketides that have been proposed to be biosynthesized from oxidative coupling of esters of two polyketidic benzoic acid derivatives. They are principally encountered in fungi and lichens. In addition to their diversified structural features, they revealed varied bioactivities such as antimicrobial, antimalarial, cytotoxic, anti-inflammatory, anti-Helicobacter pylori, antimycobacterial, antihypertensive, anti-diarrheal, antidiabetic, phytotoxic, anti-HIV, anti-osteoclastogenic, and butyrylcholinesterase, tyrosinase, hyaluronidase, and acetylcholinesterase inhibition. The current work was targeted to provide an overview on the naturally reported depsidones from various sources in the period from 2018 to the end of 2022 including their structures, biosynthesis, sources, and bioactivities, as well as the reported structure-activity relationship and semisynthetic derivatives. A total of 172 metabolites with 87 references were reviewed. The reported findings unambiguously demonstrated that these derivatives could be promising leads for therapeutic agents. However, further in-vivo evaluation of their potential biological properties and mechanistic investigations are needed.

Salazinic acid attenuates male sexual dysfunction and testicular oxidative damage in streptozotocin-induced diabetic albino rats

Male sexual dysfunctions such as infertility and impotence are recognized as the consequences of diabetes. Salazinic acid (Sa) is a depsidone found in lichen genera of Lobaria, Parmelia, and Usnea, which has prominent free radical and α-glucosidase inhibitory actions. The present study establishes the beneficial role of salazinic acid (Sa) to combat the deleterious effects of streptozotocin-induced diabetes on the male reproductive system of rats. In a dose-dependent manner, Sa significantly restored the reproductive organs weight, sperm characteristics, and testicular histoarchitecture in diabetic rats. Further, a significant recovery of insulin, follicle-stimulating hormone, luteinizing hormone and testosterone levels in serum was recorded in Sa-treated diabetic rats. The malondialdehyde levels were significantly lowered, and the activities of glutathione, superoxide dismutase, glutathione peroxidase and catalase, markedly elevated in the blood serum, as well as testicular tissue after Sa-supplementation. Sa also suppressed the protein expression levels of tumor necrosis factor-α in serum. The high dose of Sa showed significant improvement in glycemia and testicular protection, similar to sildenafil citrate. Moreover, the docking results showed that both Sa and sildenafil have a high affinity toward the target protein, PDE5 with binding affinity values found to be -9.5 and -9.2 kcal mol-1, respectively. Molecularly, both Sa and sildenafil share similar hydrogen bonding patterns with PDE5. Hence, our study clearly showed the protective role of Sa against diabetic-induced spermatogenic dysfunction in rats, possibly by competing with cGMP to bind to the catalytic domain of PDE5 and thereby controlling the oxidative impairment of testes.

Lobaric acid prevents the adverse effects of tetramethrin on the estrous cycle of female albino Wistar rats

Tetramethrin (Tm) is a commonly used pesticide that has been reported to exert estrogen-antagonistic effects selectively on female rats. The present study was undertaken to assess the protective role of lobaric acid (La) on estrous cycle in Tm-treated female Wistar rats. Female rats were exposed to Tm (50 mg/kg b.w/day) only or in combination with La at low (50 mg/kg b.w/day) or high (100 mg/kg b.w/day) dose for 30 days. The results showed that Tm altered the estrous cycle of female rats by decreasing the levels of luteinizing hormone, follicular-stimulating hormone, progesterone, estrone, and estradiol while increasing testosterone level. The morphology of vaginal smears of Tm-treated female rats showed the presence of abnormal cells and/or structures at different phases of estrus cycle. Strikingly, in (Tm + La)-treated rats, all the observed adverse effects of Tm on the hormonal parameters, cell morphology, and the length of each phase of estrous cycle were significantly diminished in a dose-dependent manner. The docking results showed that La competes with Tm for Gonadotropin-Releasing Hormone (GnRH) receptor, thereby reducing the toxicity of Tm but did not cancel the response of GnRH receptor completely. In conclusion, our results designated that La could be used as a potential candidate in the management of insecticide-induced alterations of the reproductive cycle of rodents.

Phylogenetic Studies and Metabolite Analysis of Sticta Species from Colombia and Chile by Ultra-High Performance Liquid Chromatography-High Resolution-Q-Orbitrap-Mass Spectrometry

Eleven species of lichens of the genus Sticta, ten of which were collected in Colombia (S. pseudosylvatica S. luteocyphellata S. cf. andina S. cf. hypoglabra, S. cordillerana, S. cf. gyalocarpa S. leucoblepharis, S. parahumboldtii S. impressula, S. ocaniensis) and one collected in Chile (S. lineariloba), were analyzed for the first time using hyphenated liquid chromatography with high-resolution mass spectrometry. In the metabolomic analysis, a total of 189 peaks were tentatively detected; the analyses were divided in five (5) groups of compounds comprising lipids, small phenolic compounds, saturated acids, terpenes, and typical phenolic lichen compounds such as depsides, depsidones and anthraquinones. The metabolome profiles of these eleven species are important since some compounds were identified as chemical markers for the fast identification of Sticta lichens for the first time. Finally, the usefulness of chemical compounds in comparison to traditional morphological traits to the study of ancestor–descendant relationships in the genus was assessed. Chemical and morphological consensus trees were not consistent with each other and recovered different relationships between taxa.