Sample particle size is an important parameter in the solid–liquid extraction system of natural products for obtaining their bioactive compounds. This study evaluates the effect of sample particle size on the phytochemical composition and antioxidant activity of brown macroalgae Sargassum cristaefolium. The crude ethanol extract was extracted from dried powders of S.cristeafolium with various particle sizes (> 4000 µm, > 250 µm, > 125 µm, > 45 µm, and < 45 µm). The ethanolic extracts of S.cristaefolium were analysed for Total Phenolic Content (TPC), Total Flavonoid Content (TFC), phenolic compound concentration and antioxidant activities. The extract yield and phytochemical composition were more abundant in smaller particle sizes. Furthermore, the TPC (14.19 ± 2.08 mg GAE/g extract to 43.27 ± 2.56 mg GAE/g extract) and TFC (9.6 ± 1.8 mg QE/g extract to 70.27 ± 3.59 mg QE/g extract) values also significantly increased as particle sizes decreased. In addition, phenolic compounds epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and Epigallocatechin gallate (EGCG) concentration were frequently increased in samples of smaller particle sizes based on two-way ANOVA and Tukey’s multiple comparison analysis. These results correlate with the significantly stronger antioxidant activity in samples with smaller particle sizes. The smallest particle size (< 45 µm) demonstrated the strongest antioxidant activity based on DPPH, ABTS, hydroxyl assay and FRAP. In addition, ramp function graph evaluates the desired particle size for maximum phytochemical composition and antioxidant activity is 44 µm. In conclusion, current results show the importance of particle size reduction of macroalgae samples to increase the effectivity of its biological activity.

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Marine sponge Stylissa flabelliformis is a marine sponge species that is widely found in Indonesia. Marine sponges have been proven to have pharmacological activities including wound healing, cytotoxicity and antimicrobial activity. All these activities are related to its antioxidant potential. Antioxidants are important for human health due to its ability to protect cell damage caused by free radicals. The aim of this research was to study the antioxidant activity of marine sponge (Stylissa flabelliformis) and to observe the phytochemical compound of the marine sponge such as the phenolic and flavonoid content. Extraction was performed using cold maceration with 96% ethanol solvent and continued by rotary evaporator to get the concentrated extract. Antioxidants activity was analysed using DPPH (2,2-diphenyl-1-picrylhydrazyl) method, which examines the inhibitory concentration (IC50) of the ethanol extract. Total phenolic content (TPC) was examined using Gallic acid as the standard, while total flavonoid content (TFC) was examined using quercetin as the standard. The result showed a concentration-dependent antiradical activity by reduction of DPPH with an IC50 value 2000 µg/mL. Total phenolic content was 152,67 mg GAE/g, while the total flavonoid content was 155,79 mg QE/g.

The coastal areas of Lombok has very high diversity of macroalgae which are largely unexplored. Among them are the brown macroalgae Sargassum species which are well known for their biological potentials. In this study, we aim to evaluate 4 Sargassum species, S.cristaefolium, S. crassifolium, S. polycystum, and S. aquifolium for their antioxidant potential of Sargassum species found the west coastal Aare of Lombok, Indonesia. To determine the antioxidant capacity of macroalgal extracts, 2,2-diphenyl-1-picrylhydrazyl (DPPH) as well as total phenolic content (TPC) were measured. Extracts of the brown macroalgae are well known to have very active antioxidant activity. Among them S. cristaefolium and S.crassifolium provide stronger antioxidant activity compared to S.aquifolium and S.polycystum. Furthermore, correlations were found between TPC macroalgal and their DPPH scavenging activity. This indicates an important role of polyphenols as antioxidants. Overall, brown macroalgae from Lombok coastal area may be a good source of natural bioactive compounds.