Microalgae are one of the important components in food chains of aquatic ecosystems and have been used for human consumption as food and as medicines. The wide diversity of compounds synthesized from different metabolic pathways of fresh and marine water algae provide promising sources of fatty acids, steroids, carotenoids, polysaccharides, lectins, mycosporine-like amino acids, halogenated compounds, polyketides, toxins, agar agar, alginic acid and carrageenan. This review discusses microalgae used to produce biological substances and its economic importance in food science, the pharmaceutical industry and public health.

Carotenoids are natural pigments that play pivotal roles in many physiological functions. The characteristics of carotenoids, their effects on health, and the cosmetic benefits of their usage have been under investigation for a long time; however, most reviews on this subject focus on carotenoids obtained from several microalgae, vegetables, fruits, and higher plants. Recently, microalgae have received much attention due to their abilities in producing novel bioactive metabolites, including a wide range of different carotenoids that can provide for health and cosmetic benefits. The main objectives of this review are to provide an updated view of recent work on the health and cosmetic benefits associated with carotenoid use, as well as to provide a list of microalgae that produce different types of carotenoids. This review could provide new insights to researchers on the potential role of carotenoids in improving human health.

Agsatache rugosa (Korean mint), belongs to the mint family and it has various medicinal properties. In addition, it has several valuable compounds such as monoterpenes and phenylpropanoid compounds. Amongst these, two compounds viz., rosmarinic acid (RA), and tilianin are well-known natural compounds that have numerous pharmacological properties. The phenylpropanoid biosynthetic gene expression under stress conditions and the subsequent accumulation of phenylpropanoid content has not been extensively studied in Korean mint. Here, we investigated the effect of light-emitting diodes (LEDs) on the expression levels of phenylpropanoid biosynthetic pathway genes and the accumulation of phenylpropanoid compounds such as RA and tilianin in A. rugosa. Real-time PCR analysis showed that the phenylpropanoid pathway genes responded to the LED lights. The transcript levels of downstream genes (C4H, CHS, CHI, and RAS) were comparatively higher than those of upstream genes (PAL, TAT, and HPPR). In addition, HPLC analysis showed that the content of RA and tilianin were significantly higher in plants cultivated under white light than those grown under red, blue, green, and orange lights. The RA and tilianin content were the highest in the plantlets after three weeks of exposure to white light. These results suggested that white LED lights significantly enhanced the accumulation of phenylpropanoid compounds in A. rugosa.

This study aimed to elucidate the variations in primary and secondary metabolites during Lycorisradiata flower development using high performance liquid chromatography (HPLC) and gas chromatography time-of-flight mass spectrometry (GC-TOFMS). The result showed that seven carotenoids, seven phenolic acids, three anthocyanins, and galantamine were identified in the L. radiata flowers. Most secondary metabolite levels gradually decreased according to the flower developmental stages. A total of 51 metabolites, including amines, sugars, sugar intermediates, sugar alcohols, amino acids, organic acids, phenolic acids, and tricarboxylic acid (TCA) cycle intermediates, were identified and quantified using GC-TOFMS. Among the hydrophilic compounds, most amino acids increased during flower development; in contrast, TCA cycle intermediates and sugars decreased. In particular, glutamine, asparagine, glutamic acid, and aspartic acid, which represent the main inter- and intracellular nitrogen carriers, were positively correlated with the other amino acids and were negatively correlated with the TCA cycle intermediates. Furthermore, quantitation data of the 51 hydrophilic compounds were subjected to partial least-squares discriminant analyses (PLS-DA) to assess significant differences in the metabolites of L. radiata flowers from stages 1 to 4. Therefore, this study will serve as the foundation for a biochemical approach to understand both primary and secondary metabolism in L. radiata flower development.