Chronic diseases such as cancer, diabetes, neurodegenerative and cardiovascular diseases are characterized by an enhanced state of oxidative stress, which may result from the overproduction of reactive species and/or a decrease in antioxidant defenses. The search for new chemical entities with antioxidant profile is still thus an emerging field on ongoing interest. Due to the lack of reviews concerning the antioxidant activity of lichen-derived natural compounds, we performed a review of the antioxidant potential and

Abstract:The monoterpenes are secondary metabolites of plants. They have various pharmacological properties including antifungal, antibacterial, antioxidant, anticancer, anti-spasmodic, hypotensive, and vasorelaxant. The purpose of this research was to review the cardiovascular effects of monoterpenes. The data in this resarch were collected using the Internet portals Pubmed, Scopus, and ISI Web of Knowledge between the years 1987 and 2010. In the study 33 monoterpenes were included, which were related to each of the thirteen individual words: artery, cardiovascular, heart, myocyte, vasorelaxant, vessel, hypotension, hypotensive, cardiomyocyte, ventricular, vasodilatory, aorta, and aortic. The research utilized 22 articles published mainly in the journals Phytomedicine, Fundamental Clinical Pharmacology, Planta Medica, Life Science, European Journal of Pharmacology, and Brazilian Journal of Medical and Biological Research. Of the 33 monoterpenes studied surveyed, sixteen of them had already been studied for their effects on the cardiovascular system: carvacrol, citronellol, p-cymene, eucalyptol (1,8-cineole), linalool, menthol, myrtenal, myrtenol, α-pinene, rotundifolone (piperitenone oxide), sobrerol, thymol, α-limonene, α-terpinen-4-ol, α-terpineol, and perillyl alcohol. The main effects observed were vasorelaxation, decreased heart rate and blood pressure. This review showed that the monoterpenes may be considered promising agents for prevention or treatment of diseases of the cardiovascular system.

Since its first isolation in 1844, usnic acid [2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyl-1,3(2H,9bH)-dibenzo-furandione] has become the most extensively studied lichen metabolite and one of the few that are commercially available. Lichens belonging to usnic acid-containing genera have been used as crude drugs throughout the world. There are indications of usnic acid being a potentially interesting candidate for such activities as anti-inflammatory, analgesic, healing, antioxidant, antimicrobial, antiprotozoal, antiviral, larvicidal and UV protection. However, some studies reported the liver toxicity and contact allergy. Thus, further studies are needed to establish the efficacy and safety of usnic acid.

Citronellol is an essential oil constituent from the medicinal plants Cymbopogon citratus, Cymbopogon winterianus and Lippia alba which are thought to possess antihypertensive properties. Citronellol-induced cardiovascular effects were evaluated in this study. In rats, citronellol (1-20 mg ⁄ kg, i.v.) induced hypotension, which was not affected by pre-treatment with atropine, hexamethonium, N x -nitro-L-arginine methyl ester hydrochloride or indomethacin, and tachycardia, which was only attenuated by pre-treatment with atropine and hexamethonium. These responses were less than those obtained for nifedipine, a reference drug. In intact rings of rat mesenteric artery pre-contracted with 10 lM phenylephrine, citronellol induced relaxations (pD 2 = 0.71 € 0.11; E max = 102 € 5%; n = 6) that were not affected by endothelium removal, after tetraethylamonium in rings without endothelium pre-contracted with KCl 80 mM. Citronellol strongly antagonized (maximal inhibition = 97 € 4%; n = 6) the contractions induced by CaCl 2 (10 )6 to 3 · 10 )3 M) and did not induce additional effects on the maximal response of nifedipine (10 lM). Finally, citronellol inhibited the contractions induced by 10 lM phenylephrine or 20 mM caffeine. The present results suggest that citronellol lowers blood pressure by a direct effect on the vascular smooth muscle leading to vasodilation.

We describe the antinociceptive and anti-inflammatory properties of citronellol (CT) in rodents. CT, a monoterpene alcohol, is a naturally occurring monoterpene compound prevalent in essential oils of various aromatic plant species, such as Cymbopogon citratus. In mice, when evaluated against acetic-acid-induced abdominal writhing, CT (25, 50 and 100 mg/kg, i.p.) reduced (P < 0.001) the amount of writhing compared to the control group. In the formalin test, CT also significantly inhibited both the early (neurogenic pain) and the late (inflammatory pain) phases of formalin-induced licking (P < 0.001). When assessed in a thermal model of pain, CT (100 mg/kg, i.p.) caused a significant increase (P < 0.05) in the latency response on the hot-plate test. Such results were unlikely to be caused by motor abnormality. The anti-inflammatory activity of CT was investigated through carrageenan-induced pleurisy in mice. Pretreatment with CT was able to inhibit both neutrophil infiltration and the increase in TNF-α level in the exudates from carrageenan-induced pleurisy. In in vitro experiments, CT (1 and 100 μg/ml) also decreased nitric oxide production by LPS-stimulated macrophage. Together, these results indicate that CT is effective as an analgesic compound in various pain models, with its action probably mediated by the inhibition of peripheral mediators as well as central inhibitory mechanisms that could be related to its strong antioxidant effect observed in vitro.