## 3 Results and Discussion
[46] (0.511 g GAE/kg) from studies of other _Scentesmus_ spp. In this way, the differences in the species examined could explain to some extent the above-mentioned variations in the experimental results. Moreover, [PERSON] et al. [26] used ethanol/water as extractant, while [PERSON] et al. [46] utilized ethanol. In this respect, [PERSON] et al. [26] found a nearly 5-fold difference between the yield of TPC from different extractants--water, ethanol/water, ethyl acetate and hexane. Furthermore, [PERSON] et al. [26] and [PERSON] et al. [46] applied ultrasonication as a method of extract preparation, which corresponds to this study. The TPC of _C. vulgaris_ (8.79 g GAE/kg) is consistent with the results of [PERSON] et al. [25]--8.53 g GAE/kg, but is higher than the values obtained by [PERSON] et al. [47] (3.17 g GAE/kg), [PERSON] et al. [48] (2.13 g GAE/kg) and [PERSON] et al. [46] (0.71 g GAE/kg), and much lower compared to the findings of [PERSON] et al. [49] (78 g GAE/kg). It should be noted that [PERSON] et al. [25] and [PERSON] et al. [46] used ethanol as an extractant, whereas [PERSON] et al. [48] and [PERSON] et al. [49] utilized methanol. The results of [PERSON] et al. [47] (3.17 g GAE/kg) were obtained by testing acetone extracts, which have a higher TPC yield than do methanolic (2.7-3 g GAE/kg) and ethanolic extracts (0.65 g GAE/kg). These findings again emphasize the importance of the extractant type on the yield of polyphenols. The TPC of _A. calamus_ metabolic extracts (12.83 g GAE/kg) was very similar to the findings of [PERSON] [50] (12.1 g GAE/kg) but higher than the results of [PERSON] et al. [51] (3.41-4.8 g GAE/kg) and [PERSON] et al. [52] (1.67-10.42 g GAE/kg) and lower than the data of [PERSON] and [PERSON] [53] (27 g GAE/kg), [PERSON] and [PERSON] [11] (36 g GAE/kg), and (especially) of [PERSON] et al. [10] (240.32 g GAE/kg). The aforementioned results were obtained using methanol as an extractant [10; 11; 50; 51; 52; 53]. Therefore, the major differences above should be explained by factors different from the type of solvent, such as extraction method, preparation of the sample, method of TPC determination, geographic and climatic conditions, etc. In this respect, [PERSON] and [PERSON] [11] performed the extraction of polyphenols at 60 \({}^{\circ}\)C in a horizontal water bath shaker and [PERSON] [50] likewise used maceration with a shaking condition, whereas [PERSON] et al. [51] utilized cold percolation, [PERSON] et al. [52] applied the Soxhlet method and [PERSON] [53] and [PERSON] et al. [10] used maceration. It should be noted that the major differences in the aforementioned study of [PERSON] et al. [52] were due to the various geographic and climatic conditions of 20 ecological niches in India from which _A. calamus_ was harvested. Based on the statistical data processing in this study, the altitudes were positively correlated with TPC in plants [52]. However, this conclusion was not supported by the work of [PERSON] et al. [51], who reported low TPC (3.41-4.8 g GAE/kg) from rhizome extracts from different altitudes of Uttarakhand Himalayas, India. Moreover, the TPC from the methanolic extracts of _A. calamus_ harvested from the highest altitude (1514 m) was the lowest (3.41 g GAE/kg) compared to the polyphenolic yield of _A. calamus_ methanolic extracts from lower altitudes of 344 m and 1370 m (4.1 and 4.8 g GAE/kg, respectively). In the study of [PERSON] et al. [10], methanol showed a higher polyphenol extraction potential for _A. calamus_ rhizomes and leaves compared to acetone, ethyl acetate and hexane, with up to 2-fold difference in the yield of polyphenols. [PERSON] et al. [18] found that the TPC of ethanolic extracts of _Lemma minor_ was 16.7 g GAE/kg, which was higher than the values from _L. minuta_ methanolic extracts (10.94 g GAE/kg) obtained in this study. The lack of experimental data for _L. minuta_ hindered the further comparison of TPC. Flavonoids are phenolic compounds composed of two aromatic rings linked by a unit of three carbon atoms (C6-C3-C6).