Antibacterial and Antioxidant Activity of Lichens Usnea rubrotincta, Ramalina dumeticola, Cladonia verticillata and Their Chemical Constituents

Abstract

The present study was carried out to evaluate the antibacterial and antioxidant activity of extract and chemical constituents of Usnea rubrotincta, Ramalina dumeticola and Cladonia verticillata. Acetone extract of U. rubrotincta showed promising antibacterial activity against Gram positive bacteria Bacillus subtilis with the lowest Minimal Inhibitory Concentration (MIC) value of (15.63 µg/mL). Six secondary metabolites were isolated using Preparative High Performance Liquid Chromatography (PHPLC) method from the two bioactive lichens U. rubrotincta and R. dumeticola (compound 1 -6). Among all six compounds, compound (1) exhibited strongest activity against both the tested Gram positive bacteria at 7.81 µg/mL. Compound (6) had 69.57% scavenging activity against DPPH free radical while the rest only showed below 50% scavenging activity. This is the first evaluation of antibacterial activity of lichens found in Malaysia and to our knowledge, this is the first report of antibacterial and antioxidant activity of compound (3) and (5). Keywords: antibacterial, antioxidant, Usnea rubrotincta, Ramalina dumeticola, Cladonia verticillata, usnic acid AbstrakKajian ini dijalankan bagi menilai aktiviti antibakteria dan antioksidan sebatian kimia liken yang diekstrak iaitu Usnea rubrotincta, Ramalina dumeticola dan Cladonia verticillata. Ekstrak aseton terhadap U. rubrotincta telah menunjukkan aktiviti antibakteria yang memberangsangkan terhadap bakteria Gram positif Bacillus subtilis dengan nilai Kepekatan Perencatan Minimum (KPM) sebanyak (15.63 µg/mL). Enam metabolit sekunder telah dipencilkan daripada 2 liken bioaktif iaitu U. rubrotincta dan R. dumeticola menggunakan kaedah Kromatografi Cecair Prestasi Tinggi Preparatif (KCPTP) (sebatian 1 -6). Daripada 6 sebatian, sebatian (1) telah memaparkan aktiviti yang paling kuat terhadap kedua-dua bakteria Gram positif yang dikaji pada kepekatan 7.81 µg/mL. Sebatian (6) mempunyai peratus pemerangkapan radikal bebas DPPH pada 69.57% manakala sebatian lain hanya menunjukkan aktiviti pemerangkapan kurang daripada 50%. Ini adalah penilaian pertama terhadap aktiviti antibakteria bagi liken yang dijumpai di Malaysia dan kepada pengetahuan kita, ini adalah laporan pertama bagi aktiviti antibakteria dan antioksidan sebatian (3) dan (5).

Ramalina capitata (Ach.) Nyl. acetone extract: HPLC analysis, genotoxicity, cholinesterase, antioxidant and antibacterial activity

“…The value of the total phenolics contents (TPC) of the R. capitata acetone extract was high and amounted 670.6376 ± 66.554 µg GAE mg -1 . The obtained value for the total phenol content are considerably higher than those previously published for acetone extract of Ramalina dumeticola (101.62 ± 3.51 mg GAE per g dry extract) (Gunasekaran et al, 2016[ 8 ]). Likewise, lichen from the genus Ramalina , was investigated for its phenolic content.…”

Antibacterial and Antifungal Activity of Three Ramalina Species

“…Salazinic acid was present in R. conduplicans and R. pacifica while sekikaic acid was present in R. hossei and R. conduplicans. Antimicrobial activity of usnic acid 18,35,51 , salazinic acid 52 and sekikaic acid 26,35,53 have been reported. The study of Cansaran et al 4 showed a direct correlation between the amount of usnic acid and the antimicrobial activity observed.…”

“…These compounds are called lichen substances and till now >1000 lichen secondary metabolites have been identified. Many of these compounds are low molecular weight phenolic compounds and are known to protect the lichens by functioning as sunscreen, anti-herbivore etc 21,26 . TLC is one of the techniques used to detect the secondary metabolites present in lichen extracts.…”

“…These compounds are specific to lichens and are not produced by other organisms. Extracts and purified metabolites from lichens exhibit several bioactivities such as antimicrobial, anticancer, antiviral, antioxidant, enzyme inhibitory, antiinflammatory, analgesic and antipyretic activity [16][17][18][19][20][21][22][23][24][25][26] .…”

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“…[26,58,59] In this study, the TLC showed the presence of two major compounds, viz., atranorin and zeorin. It is shown that atranorin [60][61][62] and zeorin [34] exhibit antimicrobial activity. The observed antimicrobial potential of methanolic extract of H. incana could be endorsed to the presence of these secondary metabolites.…”