Chlorella is a green unicellular alga that is commercially produced and distributed worldwide as a dietary supplement. Chlorella products contain numerous nutrients and vitamins, including D and B₁₂, that are absent in plant-derived food sources. Chlorella contains larger amounts of folate and iron than other plant-derived foods. Chlorella supplementation to mammals, including humans, has been reported to exhibit various pharmacological activities, including immunomodulatory, antioxidant, antidiabetic, antihypertensive, and antihyperlipidemic activities. Meta-analysis on the effects of Chlorella supplementation on cardiovascular risk factors have suggested that it improves total cholesterol levels, low-density lipoprotein cholesterol levels, systolic blood pressure, diastolic blood pressure, and fasting blood glucose levels but not triglycerides and high-density lipoprotein cholesterol levels. These beneficial effects of Chlorella might be due to synergism between multiple nutrient and antioxidant compounds. However, information regarding the bioactive compounds in Chlorella is limited.

• A fructosyltransferase that transfers the terminal (2 → 1)-β-linked d-fructosyl group of fructo-oligosaccharides (1^F(1-β-d-fructofuranosyl)_n sucrose, n 1) to HO-6 of the glucosyl residue and HO-1 of the fructosyl residue of similar saccharides (1^F(1-β-d-fructofuranosyl)_m sucrose, m 0) has been purified from an extract of the bulbs of onion (Allium cepa). • Successive column chromatography using DEAE-Sepharose CL-6B, Toyopearl HW65, Toyopearl HW55, DEAE-Sepharose CL-6B (2nd time), Sephadex G-100, Concanavalin A Sepharose, and Toyopearl HW-65 (2nd time) were applied for protein purification. • The general properties of the enzyme, were as follows: molecular masses of 66 kDa (gel filtration chromatography), and of 52 kDa and 25 kDa (SDS-PAGE); optimum pH of c. 5.68, stable at 20–40°C for 15 min; stable in a range of pH 5.30–6.31 at 30°C for 30 min, inhibited by Hg²⁺, Ag⁺, p-chloromercuribenzoic acid (p-CMB) and sodium dodecyl sulfate (SDS), activated by sodium deoxycholate, Triton X-100 and Tween-80. The amino acid sequence of the N-terminus moiety of the 52-kDa polypeptide was ADNEFPWTNDMLAWQRCGFHFRTVRNYMNDPSGPMYYKGWYHLFYQHNKDFAYXG and the amino acid sequence from the N-terminus of the 25-kDa polypeptide was ADVGYXCSTSGGAATRGTLGPFGLL VLANQDLTENTATYFYVSKGTDGALRTHFCQDET. • The enzyme tentatively classified as fructan: fructan 6^G-fructosyltransferase (6G-FFT). The enzyme is proposed to play an important role in the synthesis of inulin and inulinneo-series fructo-oligosaccharides in onion bulbs.

This study examined the effects of oral administration of water extract of chlorella (WEC) (100 mg/kg bodyweight) and phenethylamine (10 μg/kg bodyweight) on high-fat diet (HFD)-induced liver damage in mice. Phenethylamine significantly mitigated HFD-induced lipid oxidation (generation of malondialdehyde) and liver damage without markedly decreasing hepatic lipid accumulation. WEC exerted similar effects although with decreased efficacy. In addition, WEC and phenethylamine decreased the methylglyoxal levels and increased the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) protein levels in the liver. Methylglyoxal is generated from substrates of GAPDH, dihydroxyacetone phosphate and glyceraldehyde 3-phosphate. These facts indicate that methylglyoxal triggers oxidation of accumulated lipid, which generates malondialdehyde and consequently induces liver damage. Suppression of generation of toxic aldehydes by WEC and phenethylamine was also confirmed by maintaining hepatic cysteine, highly reactive to aldehydes. Thus, trace amounts of phenethylamine alleviate HFD-induced liver damage by regulating methylglyoxal via increase of GAPDH.

Brain-derived neurotrophic factor (BDNF) plays an important role in neurogenesis, synaptic plasticity, and cognition. BDNF is a neurotrophin that binds to tropomyosin receptor kinase B (TrkB), a specific receptor on target cell surfaces; it acts on neuronal formation, development, growth, and repair via transcription factors, such as cAMP response element-binding protein (CREB), and it is involved in learning and memory. BDNF expression is decreased in patients with Alzheimer’s disease (AD). Exercise and the intake of several different foods or ingredients can increase BDNF expression, as confirmed with lutein, xanthophylls (polar carotenoids), and ethanolamine plasmalogen (PlsEtn), which are present at high levels in the brain. This study examined the effects of combining lutein and PlsEtn using lutein-rich Chlorella and ascidian extracts containing high levels of PlsEtn bearing docosahexaenoic acid, which is abundant in the human brain, on the activation of the BDNF–TrkB–CREB signaling pathway in the hippocampus of Sprague-Dawley rats. Although activation of the BDNF–TrkB–CREB signaling pathway in the hippocampus was not observed in Chlorella or ascidian PlsEtn monotherapy, activation was observed with combination therapy at an equal dose. The results of this study suggest that the combination of Chlorella and ascidian PlsEtn may have a preventive effect against dementia, including AD.

A Chlorella powder was tested in 118 in vitro enzyme assay systems. The powder showed potent inhibitions of peptidase cathepsin S, thromboxane A₂ synthase and cyclooxygenase-2 in a dose-concentration manner with IC₅₀±standard error of the mean values of 3.46±0.93 µg/ml, 3.23±0.69 µg/ml, and 44.26±9.98 µg/ml, respectively. Other activities observed were inhibitions of tumor necrosis factor-α converting enzyme, protein tyrosine phosphatase (SHP-2), calpain, protein kinases and protein tyrosine phosphatases. Chlorella powder had no significant effect on cyclooxygenase-1. These actions to inhibit cyclooxygenase-2 and thromboxane synthase could contribute to the purported anti-inflammatory and anti-thrombotic effects of Chlorella. These results reveal important potential biochemical activities to be developed that, if confirmed by in vivo studies, might be exploited for the prevention or treatment of several serious pathologies, including inflammatory diseases, immune and cancer.