Fatty acids-carotenoid complex: An effective anti-TB agent from the chlorella growth factor-extracted spent biomass of Chlorella vulgaris

March 2020

T S Kumar 1, A Josephine 1, T Sreelatha 1, V N Azger Dusthackeer 2, B Mahizhaveni 2, G Dharani 3, R Kirubagaran 1, S Raja Kumar 4

1. Marine Biotechnology Division, National Institute of Ocean Technology, (Ministry of Earth Sciences, Government of India), Pallikaranai, Chennai, 600100, India.

2. National Institute for Research in Tuberculosis, Chetpet, Chennai, 600031, India.

3. Marine Biotechnology Division, National Institute of Ocean Technology, (Ministry of Earth Sciences, Government of India), Pallikaranai, Chennai, 600100, India. Electronic address: dhara@niot.res.in.

4. Department of Marine Biotechnology, Bharathidasan University, Tiruchirapalli, 620024, India. Electronic address: kodairaj@gmail.com.

Abstract

Ethnopharmacological relevance: The multidrug-resistant (MDR) pathogen, Mycobacterium tuberculosis, still remains as one of the major threat to mankind, despite the availability of a live attenuated vaccine and effective antibiotics. Marine microalgae, at all times, act as a key resource for valuable therapeutic compounds with limited side effects.

Aim of the study: The present explorative attempt is to isolate the biomolecules of pharmacological importance from the marine microalgae, Chlorella vulgaris, and to evaluate its effect on the ever dreadful disease, Tuberculosis. The study is also aimed to develop an economically feasible methodology for by-products extraction from microalgae.

Materials and methods: Fatty acids-carotenoid complexes (FACC), namely, FACC-1 (red oil) and FACC-2 (brown oil) were isolated, in addition to lipid and lutein from the Chlorella Growth Factor (CGF, a protein fraction enriched with vitamins, minerals and carbohydrates)-extracted spent biomass through column chromatography.

Results: FACC-1 is a complex of fatty acids such as oleic and linoleic acids, and carotenoids such as canthaxanthin and neoxanthin. FACC-2 is a complex of oleic, linoleic and linolenic acids and carotenoids (cryptoxanthin and echinenone). Initial screening for evaluation of minimum bactericidal concentration (MBC) of FACC-1 and -2 was performed against Mycobacterium tuberculosis strains such as H37Rv, SHRE sensitive clinical isolate and SHRE resistant clinical isolate. MBC was noted at 10 μg/mL by FACC-1 and at 5 μg/mL by FACC-2, determined using colony forming and Lucipherase Reporter Mycobacteriophages (LRP) assay. Testing in the PAN sensitive isolates indicated that the MBC was noted at 5 μg/mL by FACC-1 and at 2.5 μg/mL by FACC-2. Complete inhibition (100%) was observed at 100 μg/mL by FACC-1 and at 50 μg/mL by FACC-2. Testing of FACC-1 and FACC-2 individually as well as in combination on two different types of MDR strains confirmed the efficacy of the algal oils, wherein in MDR-strain 1, FACC-1 revealed 50% inhibition at 10 μg/mL, while FACC-2 exhibited the same at 5 μg/mL. Conversely, in the case of MDR strain-2, MBC of FACC-1 was at 500 μg/mL and MBCof FACC-2 to be at 250 μg/mL. No significant synergistic effect was observed on combining both the oils.

Conclusion: The study signifies the development of a potent therapeutic agent comprising of a complex of anti-TB agent (fatty acids) and antioxidants (carotenoids) from the CGF-extracted spent biomass of C. vulgaris.

Keywords: Carotenoids; Chlorella vulgaris; Linoleic acid; Linolenic acid; Mycobacterium tuberculosis; Oleic acid.