Bioactive Natural Products from Cultured Marine Microalgae and Sri Lankan Marine Algae

Abstract

Functional foods and food supplements are closely related in the manipulation of functional ingredients for the health and well-being of an individual. The reason for developing new functional foods or dietary supplements from marine bio-resources can be a growing and interesting area which can provide health enhancing ingredients in a convenient form. Therefore, it is indeed a distinct importance of the relationship between food supplements and health and well-being. Furthermore, chemically engineered food supplements are gaining interest from the view-point of their purity and containing high quality components for therapeutic uses. The marine ecosystem represents a vast and dynamic array of bio-resources attributed with its huge diversity and considered as potential untapped reservoirs for the development of functional foods for future health markets. New processing and extraction strategies of marine bio-resources integrated with biotechnology have been cherished recently. Most of the bio-molecular components, such as proteins and lipids can be extracted in large scale, using the modern and advanced biotechnological approaches, are in one hand suitable drug candidates for the pharmaceutical industry, on the other hand functional food materials for the food industry. Moreover, the furtherance of high throughput molecular biological techniques has already been incorporated with identification, mining and extraction of molecular components from marine bio-resource, rendering the promising effects. In this regard, cultured marine microalgae may be considered as a source of alternative material for new functional foods and dietary supplements. Enzyme-assisted extraction was performed on the cultured marine blue-green algae and targeted to obtain bioactive components in this study. Based on the high contents of crude proteins in the marine microalgae, commercially available protease enzymes used to isolate angiotensin I converting enzyme (ACE) inhibitory proteins and peptides from Nannochloris oculata and Chlorella ovalis, respectively. The isolated novel peptides such as Gly-Met-Asn-Asn-Leu-Thr-Pro (728.3 Da) and Leu-Glu-Gln (369.2 Da) from N. oculata showed the profound ACE inhibitory activity with IC50 values of 123 μM and 173 μM, respectively. Furthermore, purified proteins and peptides showed the increasing effect of nitric oxide (NO) level in the human umbilical vein endothelial cells (HUVECs) in vitro. In addition, molecular docking studies and in vitro digestive stability effects also were confirmed that the isolated proteins and peptides from cultured microalgae are having nutraceutical and pharmacological potency. Therefore, cultured marine microalgae proteolytic enzyme extractions can be developed for future therapeutic applications. In vitro anticancer and anti-inflammatory potentials of cultured marine microalgae including Chlorella ovalis and Nannchloropsis oculata, Phaeoductylum tricornutum and Amphidinium carterae were evaluated. Five different compounds were isolated from cultured marine diatom, P. tricornutum using the subsequence chromatographic and spectrophotometric analysis. The isolated novel fatty alcohol ester; nonyl 8-acetoxy-6-methyloctanoate (NAMO) was identified among the five isolated compounds as a strong anticancer agent. A strong suppression of cancer cells growth was observed in HL-60 and its IC50 value was 65.15 μM compared to the other cancer cells in vitro. The apoptotic occurrence in HL-60 cells by NAMO was evidenced as the accumulation of DNA in sub-G1 phase and nuclear condensations dose-dependent manner. The protein expression was revealed on the apoptotic pathway by activation of Bax and suppression of Bcl-xL as well as by up-regulation of other inducers of apoptosis, caspase-3 and p53, significantly. Anti-inflammatory effect of the isolated four out of five compounds such as 24-methylcholesta-5(6), 22-diene-3β-ol (MCDO), Cholestra-5(6), 22-dien-3, 24β-diol (CDDO), Cholestra-5(6), 22-dien-3, 24β-diol, methyl ether (CDDME) and Icosa-5, 8, 11, 14-tetraenyl acetate (ITEA) from P. tricornutum against LPS-induced RAW macrophages were evaluated. The profound nitric oxide (NO) inhibitory activities were determined by MCDO. CDDO, CDDME and ITEA against LPS-induced RAW macrophages and no cytotoxicity was observed in both LDH and MTT assays. The release of pro-inflammatory cytokines such as interleukin-1β (1L-1β), interleukin-6 (1L-6) and prostaglandin-E2 (PGE2) showed to be suppressed by MCDO and CDDO than the other isolated compounds, in a dose-dependent manner. However, tumor necrosis factor-alpha (TNF-α) production was not suppressed significantly by both compounds. In addition, suppression of the nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expressions were determined against LPS-stimulated RAW 264.7 cells significantly. Collectively, the isolated compounds from P. tricornutum exhibited the strong anti-inflammatory and anticancer activity and can be employed to develop as new lead compounds for drug discovery. For the investigation of bioactive components from Sri Lankan seaweeds, three species of red algae (Chondrophycus ceylanicus, Gelidiella acerosa, Gelidiopsis cortcata), two species of green algae (Chaetomorpha crassa, Caulerpa racemosa ) and four species of brown algae (Sargassum cassifolium, Sargassum sp. A, Sargassum sp. B and Padina commersonii) were evaluated. Among the selected brown algae, Sargassum sp. A, Sargassum sp. B and Padina commersonii were partitioned by different polar solvents and rest seaweeds were extracted only by methanol. For the bioactivity evaluations, total phenol content (TPC) and free radical scavenging activity using electron spin resonance (ESR) spectroscopy were carried out for all the fractions. In addition, sample cytotoxicity (vero cells), anti-infalmmatory (RAW macrophages) and anticancer effect against different cancer cell lines (human promyelocytic leukemia; HL-60, a human lung carcinoma; A549 and a mouse melanoma; B16F10) were assessed in vitro. In fact, most of the fractions showed the significant high activity for at least one or more bioassays, including antioxidant, anti-inflammatory and anticancer were determined. Taken together, some of the Sri Lankan seaweeds were showed the potency for the isolation of bioactive secondary metabolites using further studies.