Biochemical and Immunological implications of Lutein and Zeaxanthin

Abstract

Throughout history, nature has been acknowledged for being a primordial source of various bioactive molecules in which human macular carotenoids are gaining significant attention. Among 750 natural carotenoids, lutein, zeaxanthin and their oxidative metabolites are selectively accumulated in the macular region of living beings. Due to their vast applications in food, feed, pharmaceutical and nutraceuticals industries, the global market of lutein and zeaxanthin is continuously expanding but chemical synthesis, extraction and purification of these compounds from their natural repertoire e.g., plants, is somewhat costly and technically challenging. In this regard microbial as well as microalgal carotenoids are considered as an attractive alternative to aforementioned challenges. Through the techniques of genetic engineering and gene-editing tools like CRISPR/Cas9, the overproduction of lutein and zeaxanthin in microorganisms can be achieved but the commercial scale applications of such procedures needs to be done. Moreover, these carotenoids are highly unstable and susceptible to thermal and oxidative degradation. Therefore, esterification of these xanthophylls and microencapsulation with appropriate wall materials can increase their shelf-life and enhance their application in food industry. With their potent antioxidant activities, these carotenoids are emerging as molecules of vital importance in chronic degenerative, malignancies and antiviral diseases. Therefore, more research needs to be done to further expand the applications of lutein and zeaxanthin.

Keywords: CRISPR/Cas9; antioxidants; bioavailability; genetic engineering; lutein binding protein; macular carotenoids.

Figure 1

Global Zeaxanthin Market share by region and end use (2020–2030) with compound annual Growth rate of 8.2%. Source: (Transparency Market Research, 2020) [14].

Figure 2

A simplified schematic representation of Biosynthesis of Lutein and Zeaxanthin via both Methylerythritol4-phosphate (MEP) and mevalonate (MVA) pathway. DMAPP and IPP, precursors for α-, β-carotene are synthesized via both of these pathway. Enzymes involved in the process include: dxs: deoxyxylulose 5-phosphate synthase; dxr, deoxyxylulose 5-phosphate reductoisomerase; idi1: Isopentyl-diphosphate-isomerase 1; mva-E: Acetyl Co-A acetyl transferase.

Figure 3

Pathway showing the most preferred routes of lutein biosynthesis in Arabidopsis. Enzymatic reactions are indicated by numbers; 1: ε-cyclization by ation, 3: β-hydroxylation of carotenoids, 4: ε-ring hydroxylation, 5: β- ring hydroxylation of β, β-carotenoids by CYP97A3 (lut 5 locus). Modified from Kim et al. [26].

Figure 4

Diagram shows a proposed model for boosting carotenoid biosynthesis and antibiotic stress responses in the transgenic sweet potato plants. The upregulation of enzymes i.e., IPI (isopentyl-diphosphate delta isomerase), GGPS (Geranylgeranyl pyrophosphate synthase), PSY (Phytoene synthase), PDS (Phytoene desaturase), ZDS (Zeta-carotene desaturase), LCYE (Lycopene epsilon cyclase), ECH (Enoyl-CoA hydratase), BCH (Beta carotene hydroxylase. Modified from Kang et al. [119].

Figure 5

Computational Structure of StARD3 (PDB IB: 5I9J). Along with Ω loop, Arg 351 (shown in red sticks) is appeared to be an important amino acid residue involved in binding with lutein and allow the retention of lutein in human macula.