Constituents from Lethariella cladonioides

Two new phenolic compounds from the lichen Parmotrema cristiferum growing in Vietnam

Two new phenolic compounds, cristiferides A-B (1-2) together with six known compounds, 2,4-dihydroxyphthalide (3), lecanoric acid (4), orsellinic acid (5), 5-chloroorsellinic acid (6), methyl haematommate (7), and methyl β-orsellinate (8) were isolated from the lichen Parmotrema cristiferum (Taylor) Hale (Parmeliaceae). The structures of isolated compounds were identified from its spectroscopic data and by comparison with the literatures. Compounds 1-3 and 6-8 were evaluated for alpha-glucosidase inhibition. Compounds 2 and 7 revealed potent activity with IC₅₀ values of 72.66 μM and 48.73 μM, respectively.

Depsides: lichen metabolites active against hepatitis C virus

A thorough phytochemical study of Stereocaulon evolutum was conducted, for the isolation of structurally related atranorin derivatives. Indeed, pilot experiments suggested that atranorin (1), the main metabolite of this lichen, would interfere with the lifecycle of hepatitis C virus (HCV). Eight compounds, including one reported for the first time (2), were isolated and characterized. Two analogs (5, 6) were also synthesized, to enlarge the panel of atranorin-related structures. Most of these compounds were active against HCV, with a half-maximal inhibitory concentration of about 10 to 70 µM, with depsides more potent than monoaromatic phenols. The most effective inhibitors (1, 5 and 6) were then added at different steps of the HCV lifecycle. Interestingly, atranorin (1), bearing an aldehyde function at C-3, inhibited only viral entry, whereas the synthetic compounds 5 and 6, bearing a hydroxymethyl and a methyl function, respectively, at C-3 interfered with viral replication.

Characterisation of phenols and antioxidant and hypolipidaemic activities of Lethariella cladonioides

BACKGROUND

This study aimed to investigate the antioxidant and hypolipidaemic activities of an ethanol extract of Lethariella cladonioides (Nyl.) Krog (EE) and to characterise its chemical constituents.

RESULTS

Nine phenols were identified as canarione, thamnolic acid, squamatic acid, vermicularin, norstictic acid, baeomycesis acid, lecanoric acid, barbatinic acid and usnic acid from analysis of EE by using high-performance liquid chromatography with a diode array detector-mass spectrometry. In antioxidant analysis in vitro, the highest scavenging rate of EEs on the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, superoxide anion, hydroxyl radicals and hydrogen peroxide was 81.55 ± 1.95%, 81.84 ± 4.00%, 74.28 ± 3.71% and 74.28 ± 3.71%, respectively. Meanwhile, after administration of EE for 6 weeks in high fat/cholesterol diet mice, the most significant reduction in levels of serum triglyceride, serum total cholesterol, serum low density lipoprotein cholesterol and liver malondialdehyde were 24%, 20%, 15% and 35%, respectively. The most significant increase in levels of serum high density lipoprotein cholesterol and liver superoxide dismutase was 35% and 88%, respectively.

CONCLUSION

L. cladonioides possesses strong antioxidant and hypolipidaemic activities.

The anti-obesity effect of Lethariella cladonioides in 3T3-L1 cells and obese mice

The aim of this study was to investigate whether a water extract of L. cladonioides (LC) has an anti-obesity effect in 3T3-L1 cells and obese mice. Treatment of differentiated 3T3-L1 adipocytes with LC caused a significant increase in glycerol release and reduced the protein expression of the adipogenic transcription factors, PPARγ and C/EBPα. In an animal model, obese mice were artificially induced by a high fat diet for 10 weeks. Experimental groups were treated with LC (100 mg/kg/day) by gavage for the next 10 weeks. At the end of experiment, the body weight of the LC group mice was reduced by 14.2% compared to the high fat diet (HFD) group. The treatment also decreased liver (31.0%), epididymal (18.0%) and retroperitoneal (19.3%) adipose tissue, and kidney (6.7%) weights, respectively, compared with those of the HFD group. LC prevented diet-induced increases in the serum level of TC (22.6%), TG (11.6%), and glucose (35.0%), respectively, compared with the HFD group. However, the HDL-C level was higher in the LC group (26.1%) than the HFD group. The results of this study thus suggest that LC suppressed lipid accumulation and expression of adipogenic transcription factors, and increased the amount of glycerol release. LC also indicated an anti-obese and anti-hyperlipidemic effect.