## 4 Discussion  
The extraction yield of alginate from _S. duplicatum_ was higher in comparison with the other seaweed such as _Cystoseira barbata_, _Dictyota caribaea_ and _Padina perindusiata_ of 9.9, 7.4 and 5.4%, respectively [39; 40]. However, the extraction yield was lower than alginate from _C. implexa_ and _L. variegate_ of 29.15 and 27.57% [41], _S. angustifolium_ and _Sargassum_ sp. of 40.78 and 44.32%, respectively [42; 43]. In general, the content of alginate in various types of brown seaweed varies widely are depending on species and the method for extraction used [44]. The extraction yield and the color of alginate from _S. duplicatum_ in this study like to the previous published literature which have pale yellow color and 12% yield [40]. Based on result of characterization of alginate _S. duplicatum_, polymer of alginate _S. duplicatum_ is homogeneous because it has polydispersity index is less than two [45]. M\({}_{\rm w}\) and M\({}_{\rm n}\) of alginate of _S. duplicatum_ were lower in comparison to M\({}_{\rm w}\) and M\({}_{\rm n}\) of _S. turbinatorides_ (5.528 \(\times\) 10\({}^{5}\) and 3.852 \(\times\) 10\({}^{5}\) g/mol) and _S. vulgare_ (1.10 \(\times\) 10\({}^{5}\) and 1.94 \(\times\) 10\({}^{5}\) g/mol) [46; 47]. Alginate of _S. duplicatum_ has residue of guluronate higher than mannuronate (M/G ratio = 0.91) and also it has \(\eta\) value as 0.68 (less than 1). Hence, it indicated that alginate extracted from _S. duplicatum_ is a homopolymer block containing polyglutronate type structure [47]. The M/G ratio of alginate _S. duplicatum_ is higher than _S. fluitans_ (0.15-0.69), but lower than _S. siliquosum_ (0.70-0.94) [48]. Some other _Sargassum_ species have M/G ratio about 0.8-1.4 [25]. Quantitatively, okra fruit extracts has a total flavonoid and quercetin content higher from green okra extract of 27.0 mg/100 g and 20.03 mg (QE)/100 g [49; 50]. The green okra fruits contain of flavonoid such as a quercetin derivative. The primary flavonoids of okra fruits are up to 70% of the total antioxidant compounds [51]. Total phenolic or total flavonoids in okra extracts play an important role in the ability of antioxidant activity in varying percentages [14]. Antioxidant activity could be classified based on the IC\({}_{50}\) values, if the values less than 50 mg/mL is very strong/highly active, 51-100 mg/mL is strong/active, 101-250 mg/mL is moderate, 251-500 mg/mL is weak and more than 500 mg/mL is inactive antioxidants [38]. Okra and AOEs have strong inhibition 65.87 and 79.34, respectively in comparison with alginate of 125.31 at the same concentration. Sodium alginate from Cystoseira barbata inhibited of 174 radical scavenging activity of DPPH [12]. It showed that the antioxidant activity of alignates from different species has quite different activities, because antioxidant activity of plant extracts is associated with flavonoid or phenolic compounds in the extract and it depends on the arrangement of structural functional groups of the extracts. In addition, the existence  
Figure 9: Graph of the collagen densities. Notation on the graph shows the result of the statistical test (\(\alpha<0.05\)). (*) and (**) notation shows insignificant differences with NC, but significant differences with DC. * = 0.01 \(\leq\alpha<\) 0.05; ** = \(\alpha\leq\) 0.01. NC—normal control group; DC—diabetic control group; DA—alginate treatment group; DAO—treatment of alginate–okra fruit extracts. All groups have three variation times. of hydroxyl group, monosaccharide composition, molecular hydrogen bonds, and molecular weight affects the activity of antioxidants [52]. Some structural features of polysaccharides such as molecular weight, monosaccharide composition (block G and M), availability of hydroxyl groups, and molecular hydrogen bonds have an effect on scavenging activity.