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At least 109 records · Page 6Linked to original sources
PubMed2004

Usnic acid-induced necrosis of cultured mouse hepatocytes: inhibition of mitochondrial function and oxidative stress.

Usnic acid, a lichen acid, is a compound found in crude medicines and dietary supplements, including Lipokinetix, a supplement marketed as a weight loss agent that caused hepatotoxicity and acute liver failure in patients. In this study, we examined the toxicity of usnic acid and assessed whether usnic acid may be contributing to hepatotoxicity caused by Lipokinetix. In primary cultured murine hepatocytes, usnic acid treatment (5 microM) resulted in 98% necrosis within 16 hr (no apoptosis was detected). Usnic acid treatment was associated with early inhibition and uncoupling of the electron transport chain in mitochondria of cultured hepatocytes. This inhibition of mitochondria by usnic acid corresponded with a fall in ATP levels in hepatocytes. In isolated liver mitochondria, usnic acid was observed to directly inhibit and uncouple oxidative phosphorylation. Oxidative stress appears to be central in usnic acid-induced hepatotoxicity based on the following findings: (1) pretreatment with antioxidants (butylated hydroxytoluene+Vitamin E) decreased usnic acid-induced necrosis by nearly 70%; (2) depletion of mitochondrial GSH with diethylmaleate increased susceptibility of hepatocytes to usnic acid; (3) usnic acid treatment was associated with increase free radical generation, measured using the fluorescent probe, dichlorodihydrofluorescin. The source of reactive oxygen species after usnic acid treatment include autoxidation of usnic acid and increased hydrogen peroxide generation by mitochondria caused by usnic acid inhibition of the respiratory chain, with the latter playing a more prominent role. Taken together, our results suggest that usnic acid is a strong hepatotoxic agent that triggers oxidative stress and disrupts the normal metabolic processes of cells. Usnic acid therefore may contribute to the hepatotoxic effects of Lipokinetix and its use in any supplement must come into question.

Adenosine Triphosphate↗
PubMed1996

Lichen acids as uncouplers of oxidative phosphorylation of mouse-liver mitochondria.

Three lichen acids-namely, (+)usnic acid, vulpinic acid, and atranorin-were isolated from three lichen species (Usnea articulata, Letharia vulpina, and Parmelia tinctorum, respectively). The effects of these lichen products on mice-liver mitochondrial oxidative functions in various respiratory states and on oxidative phosphorylation were studied polarographically in vitro. The lichen acids exhibited characteristics of the 2,4-dinitrophenol (DNP), a classical uncoupler of oxidative phosphorylation. Thus, they released respiratory control and oligomycin inhibited respiration, hindered ATP synthesis, and enhanced Mg(+2)-ATPase activity. (+)Usnic acid at a concentration of 0.75 microM inhibited ADP/O ratio by 50%, caused maximal stimulation of both state-4 respiration (100%) and ATPase activity (300%). Atranorin was the only lichen acid with no significant effect on ATPase. The uncoupling effect was dose-dependent in all cases. The minimal concentrations required to cause complete uncoupling of oxidative phosphorylation were as follows: (+)usnic acid (1 microM), vulpinic acid, atranorin (5 microM) and DNP (50 microM). It was postulated that the three lichen acids induce uncoupling by acting on the inner mitochondrial membrane through their lipophilic properties and protonophoric activities.

2,4-Dinitrophenol↗
PubMed1992

Chemical Constituents of the Lichen Ramalina hierrensis.

The following compounds have been isolated from the lichen RAMALINA HIERRENSIS, collected on savin, and endemic to the Canary Islands: ursolic acid, iso-arborinol acetate, beta-sitosterol, ergosterol peroxide, cerevisterol, (-)-sandaracopimaric acid, parietin, (+)-usnic acid, (+)-iso-usnic acid, divaricatic acid, atranorin, stictic acid, gangaleodin, variolaric acid, montagnetol, and hierridin. The structures of all compounds were elucidated by physical, spectral, and chemical methods.

Journal Article↗
PubMed1993

An investigation of the allergenic constituents of Cladonia stellaris (Opiz) Pous & Vezda ('silver moss', 'reindeer moss' or 'reindeer lichen').

The sensitizing potency of Cladonia stellaris ('reindeer lichen', 'silver moss') extracts was determined in guinea pigs by a modified FCA (Freund's complete adjuvant) test. The lichen showed a moderate sensitizing potency. Similar investigations with pure common lichen constituents revealed a moderate sensitizing potency for fumarprotocetraric acid and atranorin and a weak one for evernic acid, stictic acid and both forms of usnic acid. Although generally weak, (-)-usnic acid was at least 2 x stronger than (+)-usnic acid. After separation of the Cladonia ether extract into 'usnic-acid-free' and 'usnic-acid-containing' fractions, perlatolic acid was identified as the main allergenic constituent of the 'usnic-acid-free' fraction. Stictic, evernic, fumarprotocetraric acid and atranorin were not detectable. Lichens and lichen products generally possess a weak to moderate sensitizing capacity. Compared with common sensitizers of occupational and environmental importance, these products play only a minor rôle.

Animals↗
PubMed2006

Allergic contact dermatitis from a natural deodorant: a report of 4 cases associated with lichen acid mix allergy.

BACKGROUND: Botanical ingredients used in personal care products are a significant and underreported cause of allergic contact dermatitis. OBJECTIVE: To evaluate allergic contact dermatitis from a widely-used botanical deodorant. METHODS: We conducted patch testing in four patients who were using the botanical deodorant and were referred to the contact dermatitis clinic; three patients had axillary dermatitis and one had dermatitis of the external ear. RESULTS: All four patients had positive patch test reactions to lichen acid mix and D-usnic acid. Of the three patients who were patch tested to the botanical deodorant, all had positive reactions. LIMITATIONS: We did not test to the specific lichen used in the natural deodorant but rather used our own lichen acid mix and d-usnic acid in addition to testing to the actual product. One of the patients declined to be tested with the natural deodorant, but did test positive to the lichen acid mix and d-usnic acid. CONCLUSION: Personal care products such as deodorants may represent a new route of exposure to lichen extract, a known allergen.

Adult↗