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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).

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