Mycosporine-Like Compounds in Chlorolichens: Isolation from Dermatocarpon luridum and Dermatocarpon miniatum, and their Photoprotective Properties

Abstract

!Two mycosporines were isolated for the first time in two chlorolichen species, Dermatocarpon luridum and Dermatocarpon miniatum. Mycosporine glutaminol (1) and mycosporine glutamicol (2) were isolated along with the ethyl ester of mycosporine glutamicol (3), which was formed during the purification process. Aqueous extracts and pure mycosporines were then investigated for their antioxidant activities and photoprotective properties along with their photostability and photocytotoxicity. Semi-purified mycosporine fractions were much more antioxidant than lichen aqueous crude extracts. Compound 3 (IC 50 = 4.00 µg/mL) was found to be as active as quercetin (IC 50 = 6.75 µg/mL), while the two genuine mycosporines 1 and 2 exhibited moderate activity. The three mycosporines were found to be stable until 5J/ m 2 UVA and UVB radiations whereas Trolox, used as a positive control, was degraded up to 10% and 19 %, respectively. Moreover, these mycosporines and semi-purified extracts did not induce any phototoxicity on HaCaT cells exposed to UVA radiations. Key wordsDermatocarpon luridum · Dermatocarpon miniatum · Verrucariaceae · lichen · mycosporine-like amino acids (MAAs) · photoprotectioncrude aqueous extract of D. luridum DL2:semi-purified aqueous extract of D. luridum DM1:crude aqueous extract D. miniatum DM2:semi-purified aqueous extract of D. miniatum MAAs:mycosporine-like amino acids PDA:photodiode array PIF:photo-irritancy factors Supporting information available online at http://www.thieme-connect.de/productsMycosporine-like compounds comprising mycosporines and MAAs have received much attention for their putative role in UV photoprotection as antioxidants and osmoprotectants [1][2][3][4]. Mycosporine-like compounds are small water-soluble molecules composed of cyclohexenone (oxo-mycosporine) or cyclohexenimine (imino-mycosporine) ring structures conjugated to an amino acid or an amino alcohol subunit. They are characterized by a unique strong peak in the wavelength range of 310-365 nm (ε = 28 000-50 000 M −1 · cm −1 ). About 40 mycosporines and derivatives have been described so far, and some of them are substituted with functional groups or are covalently bound to saccharidic units [5][6][7][8]. Such UV-absorbing compounds are distributed in taxonomically diverse organisms of terrestrial, marine, or freshwater origin [9]. More recently, the distribution of mycosporinelike compounds has been reported in cyanolichens (symbiotic organisms resulting from an association between a fungus and a cyanobacterium) [10,11]. Although chlorolichens correspond to 90 % of lichen species, mycosporine-like compounds have not yet been described in chlorolichens in which cyanobacteria are replaced by green algae. Their secondary metabolite profile is generally characterized by a variety of specific phenolic compounds, and most of them have UV absorbing properties [2,12]. A previous phytochemical screening revealed that chlorolichens belonging to the Dermatocarpon genus (Verrucariaceae) did not contain the usual lichen subs...

Characterization of the diversity of mycosporine-like amino acids in lichens from high altitude region of Himalaya

“…In a recent study, oxo-mycosporines from a chlorolichens were described (Nguyen et al 2015). This finding may suggest revision of the concept of a MAA occurrence specifically related to presence of cyanobacteria (La Barre et al 2014).…”

Chemical constituents of the lichen Roccella sinensis growing in Binh Thuan province

“…Moreover, careful observation of the 1 H NMR spectrum indicated that there were some minor peaks belonging to the minor compound (Z)-nostodione A [5], and the integrations of some protons indicated that the ratio of the E/Z isomers was 9/1. Up to now, nitrogen-containing compounds from lichens was very rare with reports of several compounds [1,11] and only one nitrogen-containing compound, a cyclopeptide was found in the Roccella genus [12]. This was the first time alkaloid 5 was reported as a lichen metabolite.…”

Chemical constituents of the lichen Dermatocarpon luridum and pKa value of isolated mycosporine

“…Except for compound 1, other compounds were reported for the first time in D. luridum. In the previous work, the authors have shown that mycosporine 1 has a strong absorption at 310 nm in the region of UVB (290-320 nm) with high ε 12540 M -1 .cm -1 suggesting the potential application as a natural photoprotectant [4]. Such compound contains one acido-basic site, however, its dissociation constant has never been published so far.…”

“…Previous studies revealed that instead of containing common lichen subtances as phenolic compounds, dibenzofuranes, depsides, depsidones, quinones, pulvinic acid derivatives etc., lichen species belonging to genus Dermatocarpon included several sugar alcohols as mannitol, sorbitol, volemitol and arabitol [2,3]. The first report on the occurrence of mycosporine glutaminol in the aqueous extract of D. luridum [4] prompted us that a phytochemical study on such lichen could be useful for chemical taxonomy. Recently, mycosporines have received much attention for their putative role in UV photoprotection.…”