Metabolite profiling, antioxidant, scavenging and anti-proliferative activities of selected tropical green seaweeds reveal the nutraceutical potential of Caulerpa spp

Nutraceuticals are an important ingredient of functional foods that provide health and medicinal benefits, and are recommended for daily food intake. Seaweeds are highly nutritional and considered a rich source of antioxidants, sugars, fatty acids, essential amino acids, flavonoids, phenolics, and other secondary metabolites. Green seaweeds are distributed worldwide and tropical, green algae including Caulerpa spp. could be potentially explored as a functional food. Seven abundant tropical green seaweeds (four Caulerpa species, two Ulva species, and one native Codium species) were harvested from the Saurashtra Coast (Arabian Sea, Gujarat, India) and their metabolite profiling, total flavonoid and phenolic content, and antioxidant, scavenging, reducing, and anti-proliferative activities were examined. Liquid chromatography-mass spectrometry identified remarkable metabolites, including malvidin, kaempferol, cyanidin, quercetin, apigenin, lutein, and myricetin; ninety-seven metabolites were detected by gas chromatography–mass spectrometry. Approximately forty distinct metabolites were quantified, whereas fifty-seven metabolites were detected in more than one seaweed. Fourteen unique metabolites were detected in C. scalpelliformis, which also contained notable amino acids. Caulerpa spp. (CRM: C. racemosa var. macrophysa, CRC: C. racemosa var. cornyphora, and CS: C. scalpelliformis) showed potential total antioxidant activity (>50%), and the highest potential scavenging activity (>60%) was found in CRM followed by CS and CRC extracts. CRM and CS extracts also showed maximal reducing activity (>78%). A low half maximal effective concentration (EC50) for different biochemical activities was determined for Caulerpa spp., especially CRM (total antioxidant: 150.8 ± 5.7, scavenging: 560 ± 2, and reducing: 86.4 ± 3.1 μg ml−1) compared to other select seaweeds. CRC, CRM, and CS showed significantly high total phenolic contents, 29.2 ± 2.4, 25.0 ± 3.2 and 23.8 ± 3.3 mg gallic acid equivalent (GAE) g−1 extract, respectively. Similarly, a high total flavonoid content was detected in CS (769 ± 33 mg quercetin-equivalent g−1 extract) followed by CRC (562 ± 44), and CRM (523 ± 60). All activities (total antioxidant, scavenging, and reducing) were positively correlated with each other and also with total phenolic and flavonoid contents. Principal component analysis confirmed that CRC is a rich source of phenolic and flavonoid compounds, whereas CS and CRO (C. racemosa var. occidentalis) possessed higher total antioxidant, scavenging, and anti-proliferative activities compared to the other selected seaweeds. The study revealed that Caulerpa spp. are a promising functional food ingredient and could be explored as daily dietary supplements.