B. C. Behera

Antioxidative and cardiovascular-protective activities of metabolite usnic acid and psoromic acid produced by lichen species Usnea complanata under submerged fermentation

Context: Lichens have been used for various purposes such as dyes, perfumes and remedies in folk medicine indicating the pharmaceutical potential of lichens. Objective: Lichen growth in nature is very slow. To overcome this major drawback, we standardized the culture media to culture the lichen Usnea complanata (Müll.Arg.) Motyka (Parmeliaceae) for (1) in vitro synthesis of natural lichen substances, and (2) determination of antioxidative and cardiovascular-protective activity of usnic acid and psoromic acid. Materials and methods: Lichen U. complanata has been cultured in fermentor under submerged condition. Antioxidative and cardiovascular-protective activity of the extract and the purified lichen substances usnic and psoromic acid have been determined. Results: Except methanol, all other extracts exhibited antioxidative action in terms of free radical scavenging activity (FRSA) with a half-inhibiting concentration (IC50) value of 22.86 to 25.0 µg/mL, nitric oxide radical scavenging activity (NORSA) 141.3 to 149.1 µg/mL and for lipid peroxidation inhibition (LPI) 125 to 157.9 µg/mL. Usnic acid or psoromic acid showed antioxidative action with IC50 values ranging from 0.174 to 0.271 mg/mL. Methanol and ethyl acetate extract showed hydroxy-3-methyl-glutaryl-CoA reductase (HMGR) inhibition of 65.18 to 74.81%. Only 43.47% inhibition of angiotensin converting enzyme (ACE) was shown by methanol extract. Usnic acid showed noncompetitive type of HMGR inhibition and uncompetitive type of ACE inhibition. Psoromic acid exhibited competitive type of HMGR inhibition and mixed type of ACE inhibition. Discussion: U. complanata showed both cardiovascular-protective and antioxidant properties. The lichen species U. complanata may be a natural bioresource for possible pharmaceutical applications.

Inhibitory activity of xanthine oxidase and superoxide-scavenging activity in some taxa of the lichen family Graphidaceae

Results on the screening of species of the lichen family Graphidaceae for superoxide-scavenging activity (SSA) and xanthine-oxidase inhibitory (IXO) activity have been presented. The potential of the extracts for scavenging of superoxide and inhibition of xanthine-oxidase under various physiological conditions has been evaluated. The methanolic extracts of the species of family Graphidaceae showed inhibitory properties of xanthine oxidase (IC50 = 2.0 to 5.26 microg/ml) with an additional superoxide scavenging capacity (IC50 = 3.63 to 13.88 microg/ml). The potential of the methanolic extracts for scavenging of superoxide and inhibition of xanthine oxidase remained stable at 4 degrees C. Thus the extracts can be maintained for longer periods for their therapeutic uses.

Tyrosinase-inhibitory activity in some species of the lichen family Graphidaceae.

Twenty-five species of the lichen family Graphidaceae have been investigated for tyrosinaseinhibitory activity. Tyrosinase-inhibiting material was extracted with solvents methanol, acetone, ethanol, dimethyl sulphoxide in water, and with water only. Methanol has been found to be suitable for extracting adequate amounts of tyrosinaseinhibiting component from the natural thallus. The lichen species such as Graphina glaucorufa, Graphina multistriata, Graphina salacinilabiata, Graphis assamensis, Graphis nakanishiana, and Phaeographopsis indica, have shown inhibition of tyrosinase over a range of 30-78%. Half-inhibiting concentration (IC50, J.g/ml) has been found to be much lower than the standard tyrosinase inhibitors and thus can compete with other commercially available tyrosinase inhibitors. The extracts of these species have been found to be stable at 4°C.

Radical scavenging, prolyl endopeptidase inhibitory, and antimicrobial potential of a cultured Himalayan lichen Cetrelia olivetorum.

Abstract Context: Lichens are source of natural bioactive compounds which are traditionally used to cure a variety of ailments. Objective: The objective of this study is to assess free radical scavenging, prolyl endopeptidase inhibitory (PEPI), and antimicrobial potential of a high altitude lichen species Cetrelia olivetorum (Nyl.) W. L. Culb. & C. F. Culb (Parmeliaceae). Materials and methods: Lichen C. olivetorum has been cultured in vitro, and optimized culture conditions were implemented in bioreactor to obtain high quantity of biomass for the study of radical scavenging, PEPI, and antimicrobial activities. Radical scavenging activity of methanol extract of Cetrelia olivetorum (MECO) was tested at 100 µg/mL, PEPI activity at 25 and 50 µg/mL, and antimicrobial activity at 5, 25, 50, and 100 µg/mL conc. All the biological activities of natural thallus extract and its derived culture extract were evaluated spectrophotometrically. Results: Murashige and Skoog medium supplemented with 3% glucose and 100 ppb indole-3-butyric acid (IBA) supported biomass growth at flask level and yielded 5.095 g biomass in bioreactor. MECO of both the cultured and the natural lichen exhibited half inhibiting concentration (IC50) for radical scavenging activities in the range of 50–60 µg/mL, whereas the IC50 value of standard antioxidants was found to be in the range of 12–29 µg/mL. The IC50 value of lichen extract for PEPI activity was 144–288 µg/mL, whereas the IC50 value of standard prolyl endopeptidase inhibitor, Z-pro-prolinal, was 57.73 µg/mL. As far as the antimicrobial activity of MECO is concerned, minimum inhibitory concentration (MIC) value of lichen extracts against tested microorganisms was obtained in the range of 50–104 µg/mL and found to be more effective than commercially available standard erythromycin. Discussion: Murashige and Skoog medium containing IBA was found to be suitable for maximum biomass production of C. olivetorum under bioreactor conditions. The cultured lichen biomass extract also showed antioxidant, PEPI, and antimicrobial potential. Conclusion: The present study indicates therapeutic potential of Himalayan lichen C. olivetorum against neurodegenerative diseases owing to its radical scavenging, PEPI, and antimicrobial activities. Further, the result encourages its commercial exploitation through mass culture for production of its bioactive components and their use in pharmaceutical and nutraceutical industries.

Future Directions in the Study of Pharmaceutical Potential of Lichens

Lichens are a stable self-supporting symbiotic organism, composed of a fungal and an algal partner. In this symbiotic form, lichens produce a number of unique secondary metabolites through various biosynthetic pathways, namely, acetyl polymalonyl, shikimic acid and mevalonic acid pathways. Most of the lichen substances are phenolic compounds and are reported to have wide variety of biological actions: antioxidant, antimicrobial, antiviral, anti-inflammatory, analgesic, antipyretic, antiproliferative and cytotoxic effects. Acetyl polymalonyl-derived polyketide compounds, depsides, depsidones, dibenzofuranes, xanthones and naphthaquinones, are of great interest. Compounds from other pathways are esters, terpenes, steroids, terphenylquinones and pulvinic acid. Although manifold biological properties of lichen secondary metabolites have been recognized, their pharmaceutical potential has not been fully explored due to their slow growing nature and difficulties in their artificial cultivation. Many researchers are still working hard to discover and identify the novel lead compounds from lichens. In this chapter, attention has been given to bring in notice some pharmaceutically important lichens and their secondary metabolites and to provide a direction for the study of lichen prospect.

Protoplast isolation from cultured lichen Usnea ghattensis, their fusion with protoplasts of Aspergillus nidulans, fusant regeneration and production of usnic acid

Protoplasts isolated from the mycobiont of a cultured lichen Usnea ghattensis were fused with protoplasts of the fungus Aspergillus nidulans in order to increase the growth rate of the cultured lichen mycobiont in vitro. The maximum protoplast yield (102 × 104/g fresh cell mass) was reached in citrate buffer with 50 mmol/L 2-sulfanylethanol (‘2-mercaptoethanol’) containing 0.1 % Novozym after 1.5 h at pH 5 and ≤25 °C. The increase in the concentration of the above effectors or the addition of others (e.g., MgSO4) as well as increase in time, shaking frequency, etc. caused the lower yield of protoplasts. The fused protoplasts were regenerated after transfer to malt extract-yeast extract medium and produced, after a 45-d cultivation, a fresh cell mass of 0.232 g (from starting 0.3 g) along with the lichen substance usnic acid.

Antioxidative, Cardioprotective, and Anticancer Potential of Two Lichenized Fungi, Everniastrum cirrhatum and Parmotrema reticulatum, from Western Ghats of India

ABSTRACT The antioxidative, cardioprotective, and anticancer potential of extracts of the edible lichens Everniastrum cirrhatum and Parmotrema reticulatum were evaluated. Acetone extracts of P. reticulatum exhibited nitric oxide scavenging and anti-lipid peroxidation in the range of 35.0–97.0%. IC50 values of extracts for angiotensin-converting enzyme and HMG-CoA reductase inhibition were observed in the range of 97–375 µg.mL–1 and 89–118 µg.mL–1, respectively, against standard inhibitors captopril (32 µg.mL–1) and pravastatin (26 µg.mL–1); methanol extract of P. reticulatum displayed the highest cytotoxicity, reducing HCT-116 cell viability to 40%, suggesting potential use of these lichens as nutraceuticals.

In Vitro Culture of Lichen Partners: Need and Implications

In the world, lichens are slowest growing symbiotic organism associations between fungi and a photosynthetic alga and/or cyanobacteria. Lichens produce a wide array of secondary metabolites which are unique and forms under lichenized conditions. Secondary metabolites of lichens demonstrated significant inhibition of various biological activities at very low concentrations. Although lichens are reservoir for various biologically active compounds, only few lichens and their compounds have been tested for their biological significance and still there are many more yet to be tested. Hence, there is clearly an urgent need for expanding research in this area including in-depth studies of those compounds which have shown promising results. A strong focus is also needed on the most promising lichen-based drug therapies followed by large scale production of the best of those compounds. One of the main issues related to the limited use of lichen compounds in modern medicine is the slow growth rate of lichen thalli which remains as a challenge to enhance their biomass with in vitro culture. Advance research in the field of cultivating lichens and their symbionts will enable the mass production of lichen substances and their pharmaceutical applications. The present review on tissue culture of lichens of various groups, biosynthesis of their unique secondary compounds, physiological conditions required for their synthesis, and biological activities will significantly contribute to the present knowledge in the field of experimental lichenology and will also attract the attention of industry/society/nation as a whole.