Chemical composition and molecular structure of polysaccharide-protein biopolymer from Durio zibethinus seed: extraction and purification process

Abstract

Background: The biological functions of natural biopolymers from plant sources depend on their chemical composition and molecular structure. In addition, the extraction and further processing conditions significantly influence the chemical and molecular structure of the plant biopolymer. The main objective of the present study was to characterize the chemical and molecular structure of a natural biopolymer from Durio zibethinus seed. A size-exclusion chromatography coupled to multi angle laser light-scattering (SEC-MALS) was applied to analyze the molecular weight (Mw), number average molecular weight (Mn), and polydispersity index (Mw/Mn).

Results: The most abundant monosaccharide in the carbohydrate composition of durian seed gum were galactose (48.6-59.9%), glucose (37.1-45.1%), arabinose (0.58-3.41%), and xylose (0.3-3.21%). The predominant fatty acid of the lipid fraction from the durian seed gum were palmitic acid (C16:0), palmitoleic acid (C16:1), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), and linolenic acid (C18:2). The most abundant amino acids of durian seed gum were: leucine (30.9-37.3%), lysine (6.04-8.36%), aspartic acid (6.10-7.19%), glycine (6.07-7.42%), alanine (5.24-6.14%), glutamic acid (5.57-7.09%), valine (4.5-5.50%), proline (3.87-4.81%), serine (4.39-5.18%), threonine (3.44-6.50%), isoleucine (3.30-4.07%), and phenylalanine (3.11-9.04%).

Conclusion: The presence of essential amino acids in the chemical structure of durian seed gum reinforces its nutritional value.

Figure 1

HPLC chromatograms showing the sugar profile of aqueous (a) and chemically (b)-extracted durian seed gums.

Figure 2

The percentage of xylose and arabinose (a) as well as glucose and galactose (b) in crude and different purified durian seed gums (A: isopropanol and ethanol; B: isopropanol and acetone; C: saturated barium hydroxide; D: Fehling solution); Mean ± standard deviation; a-c: Significant (p < 0.05) difference among samples in terms of xylose and glucose; A-D: Significant (p < 0.05) difference among samples in terms of arabinose and galactose.

Figure 3

Fatty acid profile of the lipid fraction from (a) aqueous crude gum, (b) chemical crude gum, and (c-f) purified seed gums (a-d); C16:0 (palmitic acid), C16:1 (palmitoleic acid), C18:0 (stearic acid), C18:1 (oleic acid), C18:2 (linoleic acid), C18:2 (linolenic acid), and C20:0 (arachidic acid).

Figure 4

Amino acid profile of (a) crude gum, (b) purified gum a, (c) purified gum b, (d) purified gum c, (e) purified gum d; aspartic acid (Asp), glutamic acid (Glu), serine (Ser), glycine (Gly), histidine (His), arginine (Arg), threonine (Thr), alanine (Ala), proline (Pro), internal standard (IS, alpha amino butyric acid), tyrosine (Tyr), valine (Val), methionine (Met), isoleucine (Ile), leucine (Leu), phenylalanine (Phe), and lysine (Lys).