Protein nutritional quality, amino acid profile, anti-amylase and anti-glucosidase properties of microalgae: Inhibition and mechanisms of action through in vitro and in silico studies

Highlights

• Nutritional, anti-amylase and anti-glucosidase properties of microalgae examined.

• Non-essential, non-protein, and flavour amino acids in microalgae were greater than egg protein.

• Essential and sulfur amino acids im microalgae were lower than egg protein.

• Microalgae amino acid exhibited good anti-amylase and anti-glucosidase properties.

• Microalgae amino acids inhibited amylase and glucosidase by increasing the Km/Vmax ratio.

Abstract

Since microalgae proteins contain the same amount of protein as conventional protein sources such as soybean, milk, beef, and egg, they are considered as new sources of functional amino acids. In this research, microalgae amino acid extracts were studied for their nutritional value as well as their anti-amylase and anti-glucosidase properties, in vitro and in silico. Essential, non-essential, non-protein, flavor, hydrophobic, aromatic, bitter, and sweet amino acids were found to be equal to or greater than those found in egg protein in the selected microalgae. The anti-amylase and anti-glucosidase properties of amino acid extract were confirmed in this study, but at a lower level than acarbose. Microalgae amino acids inhibited amylase and glucosidase by increasing the K_m/V_max ratio through non-competition and un-competition strategy, according to the kinetic analysis. Molecular docking analysis revealed that microalgae amino acids interact with amino acid residues near the active site of amylase and allosteric sites of glucosidase through p-alkyl interactions, positive-negative interactions, salt bridges, and hydrogen bonds. In conclusion microalgae amino acid not only can be considered as functional food with nutritional quality equal to egg protein, but also due to functional amino acid can be imperative as non-competitive and un-competitive inhibitor of amylase and glucosidase.

Introduction

Proteins derived from plants and animals are currently the most important sources of protein in food and feed. Expanding cultivation areas, increasing cropping frequencies, and increasing yields are all necessary to meeting the food demand. Other low-cost and readily available protein sources are needed because of increased global pollution and a scarcity of animal and plant protein supplies (Smetana, Sandmann, Rohn, Pleissner, & Heinz, 2017). As a new and accessible resource of proteins, microalgae are relatively recent concept. Many types of microalgae have the same amount of protein as traditional protein sources like soybean, milk, beef, and egg (Niccolai, Zittelli, Rodolfi, Biondi, & Tredici, 2010). In addition to its dietary value, usefulness, and efficiency, microalgae as a protein source has a number of environmental benefits, including low land requirements, the use of non-arable land for cultivation, reduced freshwater consumption, the potential to grow in seawater, and the ability to substitute non-arable land for cultivation (Caporgno & Mathys, 2018).

While there has been some research about the use of microalgae-derived peptides and amino acids in novel functional food products in recent years, much of the available literature highlights the contribution of whole microalgae cells to food (Tang et al., 2020). Spirulina and Chlorella provide high-grade proteins, with well-proportioned amino acid profiles that meet WHO/FAO/UNU standards for essential amino acid for humans feeding (Bleakley & Hayes, 2017). A few microalgae-derived molecules, along with peptides and amino acids, have been linked to antioxidative (Zhu, Zhao, Zhang, Liu, & Ao, 2020), anti-hypertensive (Caporgno & Mathys, 2018), anti-cancerogenic (Chalamaiah, Yu, & Wu, 2018), hepato-protective (Senthil-kumar et al., 2018), and anti-diabetic (Lauritano et al., 2016) activities.

Diabetes mellitus (DM) is characterized by relative insulin deficiency or insulin resistance. Inhibiting the digestion of dietary carbohydrates to reduce glucose reabsorption in the intestine through inhibiting carbohydrate-degrading enzymes, glucosidase and amylase, is one of the clinical methods in the management of DM. Present amylase and glucosidase inhibitors in therapeutic use, such as acarbose, voglibose, and miglitol, have been linked to bloating, stomach pain, diarrhea, and flatulence. As a result, there is a pressing need for complementary and alternative medicines with less side effects that can be used in combination with DM treatment (Vieira et al., 2019). Nonetheless, there is a scarcity of studies on the anti-diabetic potential of microalgae amino acid, and the evidence for practical ability benefits of these amino acids is weak. Furthermore, the ways behind their anti-diabetic effects have not been investigated.

The aim of this study is to learn more about amino acid composition and nutritional quality of Chlorella vulgaris, Scenedesmus oblique, Chlamydomonas reinhardtii, Haematococcus pluvialis, Monoraphidium dybowskii, and Parachlorella kessleri. The anti-diabetic potential of the amino acid extract against amylase and glucosidase activities was investigated. The potential inhibition mechanism of microalgae amino acid on the amylase and glucosidase was investigated using enzymatic kinetic analysis. Furthermore, molecular docking analysis was also used to simulate the interactions between microalgae amino acid with amylase and glucosidase.