Melanins are black or brown pigments of high molecular weight formed by oxidative polymerization of phenolic or indolic compounds. They are found in organisms of all phylogenetic kingdoms, showing a broad spectrum of biological roles, including thermoregulation, chemoprotection, camouflage and sexual display. 1) These pigments are not essential for fungal growth and development, but have been reported to act as "fungal armor" because of the ability of the polymer to protect these microorganisms against harmful environmental conditions such as UV radiation, temperature extremes, hydrolytic enzymes, metals or plant defense mechanisms. [2][3][4][5][6][7] The effect of melanin enhancing the survival of fungi can be mainly due to its function as an extracellular redox buffer which can neutralize oxidants generated by environmental stress. 8) Wang and Casadevall 9) observed that melanized Cryptococcus neoformans cells survived the action of nitrogen-and oxygen-derived oxidants approximately 10-fold better than did non-melanized cells, suggesting that melanin contributes to virulence by protecting pathogens against free radicals generated immunologically. Studies on oxidative damage have shown that melanin in Wangiella dermatidis and Alternaria alternata appeared to confer cellular redox properties similar to those conferred by melanin upon C. neoformans. 10,11) Hoogduijn et al. 12) observed that melanin protects melanocytes and keratinocytes from the induction of DNA strand breaks by hydrogen peroxide, indicating that this pigment has an important antioxidant role in the skin.In the last decades, skin cancer has been increasing alarmingly due to chronic exposure to UV light and certain environmental chemicals. The major cause of DNA damage induced by these agents is the production of reactive oxygen species (ROS) and free radicals. 13,14) Substances acting as antioxidants, i.e., reactive oxygen and radical scavengers, protect cells from ROS-mediated DNA damage, which can result in mutation and subsequent carcinogenesis. 15,16) Various studies have demonstrated that melanins act as antioxidants and suggest its use as a raw cosmetic material to minimize light-and toxin-induced tissue destruction. 1,17) In this context, fungal melanin is of considerable biotechnological interest because it can be produced for low cost on a large scale compared with industrially-produced melanin, making its use as an antioxidative agent in cosmetic formulations economically advantageous. Taking this information into account, in the present study we assessed the antioxidant activity of the melanin pigment extracted from A. nidulans fungus in order to determine its possible utilization in the pharmaceutical industry. RESULTS AND DISCUSSIONWe first assessed the antioxidant activity of synthetic melanin, which was used as a control in the study because of its recognized activity as a reactive oxygen species (ROS) scavenger 5) As shown in Tables 1 and 2, the oxidation of 5-thio-2-nitrobenzoic acid (TNB) by hydrogen peroxide (H 2 O 2 ) and h...

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Spondias mombin L. is used in folk medicine for the treatment of inflammation and gastrointestinal diseases. Our study investigated the antiulcer activity of S. mombin ethanolic extract (SmEE) and its majority compounds gallic acid (GA) and ellagic acid (EA). Phytochemical characterization was performed by HPLC. The SmEE was screened for in vitro antioxidant activities using phosphomolybdenum, ABTS, DPPH, and FRAP assays. The antiulcer activity of SmEE, GA, EA, or GA + EA was evaluated by gastric lesion models induced by absolute ethanol and indomethacin. Following this, it is capable of stimulating mucus production, antisecretory capacity, and the influence of −SH groups and NO in the effect of SmEE. Its healing activity was demonstrated by acetic acid-induced chronic ulcer model. Anti-Helicobacter pylori activity was assessed by determining the MIC of the SmEE (64–1024 μg/mL). The HPLC results identified the presence of gallic acid and ellagic acid in SmEE. The extract showed antioxidant activity in vitro. SmEE (50, 100, and 200 mg/kg) reduced the area of ulcerative lesions induced by ethanol in 23.8, 90.3, and 90.2%, respectively. In NSAID model, the SmEE induced protection of 36.8, 49.4, and 49.9%, respectively. GA (10 mg/kg) or EA (7 mg/kg) or the association of GA + EA (10 + 7 mg/kg) inhibited the ethanol-induced lesions in 71.8, 70.9, and 94.9%, respectively, indicating synergistic action. SmEE (100 mg/kg) decreased acid secretion and H+ concentration in the gastric contents, increased levels of mucus, and showed to be dependent of −SH groups and NO on the protection of the gastric mucosa. In chronic ulcer model, SmEE reduced the gastric area lesion. SmEE showed anti-H. pylori activity. In conclusion, our study showed that SmEE has antiulcerogenic activity. GA and EA are isolated gastric protectors and, when associated, acted synergistically to protect the gastric mucosa.

Ethnomedicinal studies in the Amazon community and in the Northeast region of Brazil highlight the use of Libidibia ferrea fruits for the treatment of gastric problems. However, there are no data in the literature of this pharmacological activity. Thus, the aim of this paper is to provide a scientific basis for the use of the dry extract of L. ferrea pods (DELfp) for the treatment of peptic ulcers. Phytochemical characterization was performed by HPLC/MS. In vitro antioxidant activity was assessed using DPPH, ABTS, phosphomolybdenum, and superoxide radical scavenging activity. The gastroprotective activity, the ability to stimulate mucus production, the antisecretory activity, and the influence of -SH and NO compounds on the antiulcerogenic activity of DELfp were evaluated. The healing activity was determined by the acetic acid-induced chronic ulcer model. Anti-Helicobacter pylori activity was investigated. HPLC/MS results identified the presence of phenolic compounds, gallic acid and ellagic acid, in DELfp. The extract showed antioxidant activity in vitro. In ulcers induced by absolute ethanol and acidified ethanol, the ED50 values of DELfp were 113 and 185.7 mg/kg, respectively. DELfp (100, 200, and 400 mg/kg) inhibited indomethacin-induced lesions by 66.7, 69.6, and 65.8%, respectively. DELfp (200 mg/kg) reduced gastric secretion and H+ concentration in the gastric contents and showed to be independent of nitric oxide (NO) and dependent on sulfhydryl (-SH) compounds in the protection of the gastric mucosa. In the chronic ulcer model, DELfp reduced the area of the gastric lesion. DELfp also showed anti-H. pylori activity. In conclusion, DELfp showed antioxidant, gastroprotective, healing, and antiulcerogenic activities. The mechanism of these actions seems to be mediated by different pathways and involves the reduction of gastric secretion and H+ concentration, dependence on sulfhydryl compounds, and anti-H. pylori activity. All these actions support the medicinal use of this species in the management of peptic ulcers.

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The Helicobacter pylori bacterium is one of the main causes of chronic gastritis, peptic ulcers, and even gastric cancer. It affects an average of half of the world population. Its difficult eradication depends upon multi-drug therapy. Since its classification as a group 1 carcinogenic by International Agency for Research on Cancer (IARC), the importance of H. pylori eradication has obtained a novel meaning. There is considerable interest in alternative therapies for the eradication of H. pylori using compounds from a wide range of natural products. In the present study, we investigated the antibacterial property of the isocoumarin paepalantine against H. pylori and it exhibited significant anti-H. pylori activity at a minimum inhibitory concentration (MIC) of 128 μg/mL and at a minimum bactericidal concentration (MBC) of 256 μg/mL. The scanning electron microscopy (SEM) revealed significant morphological changes of the bacterial cell as a response to a sub-MIC of paepalantine, suggesting a penicillin-binding protein (PBP) inhibition. Computational studies were carried out in order to study binding modes for paepalantine in PBP binding sites, exploring the active and allosteric sites. The data from the present study indicates that paepalantine exhibits significant anti-H. pylori activity, most likely by inhibiting membrane protein synthesis.

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