Study on natural pigment of Carotenoid and Chlorophyll content in five species of Malaysian seaweed

Abstract

Seaweed, also known as macroalgae, are plant-like organisms that can be found in marine habitat. Various seaweed species have been gaining the interest of researchers due to the presence of functional bioactive compounds that can be extracted from their biomass. The study was conducted because of major colorants that have been used in the industries are derived from synthetic colorants. It is due to the comparative stability, cost effective and ease of use. Safety of the synthetic colorant usage is still being debated in order to identify the harmful effect towards the consumption. In the present study, three varieties of red macroalgae (Eucheuma denticulatum , Glacilaria tikvahiae and Kappaphycus striatum), a green macroalgae (Caulerpa lentillifera) and one brown macroalgae (Padina pavonica) were selected to determine their chlorophyll and carotenoid content by using UV-Vis spectrophotometer and HPLC, to identify their antioxidant properties by using DPPH scavenging method and antimicrobial activity by using Disc-diffusion method as well as to assess the stability of their natural pigment via CIELab. Characterisation study of the functional groups and volatile compounds in the selected seaweed were performed by using FTIR and GC-TOF/MS instrument. The findings of this research represents the preliminary stage in this study. Overall results for GC-TOF/MS analysis lead to the identification of 37 compounds K. striatum, 32 compounds from in both E. denticulatum and P. pavonica as well as 27 compounds in C. lentillifera and G. tikvahiae. In terms of carotenoid content, P. pavonica contained the highest amount of carotenoid (100.9 ± 14.7 µg/g DW) while G. tikvahiae recorded the lowest value (25.1 ± 9.4 µg/g DW). Meanwhile, individual carotenoid content showed K. striatum had the highest lutein content (38.6 µg/g DW) while P. pavonica showed the lowest lutein content (7.2 µg/g DW). As for zeaxanthin, C. lentillifera (21.3 µg/g DW) showed the highest amount while E. denticulatum (3.6 µg/g DW) showed the lowest result. C. lentillifera also contained the most beta-carotene (10.7 µg/g DW) whereas E. denticulatum had the least amount at (2.4 µg/g DW). Last but not least, violaxanthin was only found in the green seaweed C. lentillifera (8.9 µg/g DW). The total chlorophyll content for C. lentillifera and P. pavonica were comparable at (7.3 µg/g DW) and (7.5 µg/g DW) respectively. In contrast, E. denticulatum recorded the lowest amount of total chlorophyll content at (2.9 µg/g DW). The antioxidant test showed that P. pavonica presented the strongest DPPH activity with percentage of inhibition (i%) of (61.0% ± 0.9) while K. striatum showed the weakest DPPH activity (35.6% ± 1.7). In the antimicrobial test, the strong antimicrobial action was shown by all the seaweed samples toward E. coli and P. aerugenosa. Moderate activity was observed in all seaweed extracts against MRSA and S epidermidis. S. pyogenes and B. subtilis were least affected by all seaweed samples. Besides that, the overall results of the antifungal test demonstrated moderate antifungal action by all seaweed samples towards M. gypseum and Fusarium sp. In the stability study, it was evident that the difference in salinity for every seaweed sample concentration was consistent from week 1 up to week 4. In terms of pH, seaweed colour change were more obvious in acidic condition compared to neutral and alkaline condition. Higher temperature also led to rapid colour changes in seaweed pigments. Finally, it was found that the colour changes in seaweed increased with longer exposure to UVA and UVB. As a conclusion, all the seaweed selected in this study possess bioactive compounds that have the potential to be utilized in various fields.