Development of HP-TLC method for rapid quantification of sugars, catechins, phenolic acids and saponins to assess Yam (Dioscorea spp.) tuber flour quality

Abstract

Eight yam species (Dioscorea spp.) represented by 522 accessions (landraces and hybrids) were analysed for the individual sugars, catechins, phenolic acids and saponins contents of their tuber flours. Maltose, sucrose, glucose and fructose were quantified. Reducing sugars mean values were highly variable within species and ranged from 0.16%dry weight (DW) (SD ± 0.12) in D. dumetorum to 3.15%DW (±2.49) in D. esculenta. Maltose was detected only in D. esculenta. Chlorogenic acid, gallic acid and other phenolic acids ranged from 4.33 mg/g DW in D. bulbifera to 4.87 mg/g in D. alata and 9.55 mg/g in D. nummularia but were not detected in other species. Catechins (epicatechin and catechin) were highest in D. bulbifera bulbils (25.18 mg/g) and tubers (6.96 mg/g), and lowest in D. esculenta (0.32 mg/g). Their content is significantly correlated with dark flour colour and they most likely contribute to the oxidation of tuber flesh. Saponins (dioscin and gracillin) were quantified in only two species: D. cayenensis (5.94 mg/g, SD ± 3.78) and D. esculenta (3.74 mg/g, SD ± 3.72). Varietal selection may tend to reduce sugars levels and increase secondary metabolites with bioactive properties. HP-TLC is a suitable technique for the rapid quantification of compounds related to yam tuber flour quality.

Review of empirical and emerging breeding methods and tools for yam (Dioscorea spp.) improvement: Status and prospects

“…High‐performance thin‐layer chromatography (HP‐TLC) is a novel technology for rapid nutritional analysis of multiple samples at a lower cost compared to column chromatography. Lebot, Malapa, and Molisalé () have recently developed and optimized an HP‐TLC protocol for the rapid quantification of individual sugars, allantoin, phenolic acids, catechins and saponins in yam tuber flours. This technique was successfully used for the rapid quantification of compounds related to tuber flour quality of 522 accessions of eight Dioscorea species.…”

Carbohydrate and bioactive compounds composition of starchy tropical fruits and tubers, in relation to pre and postharvest conditions: A review

“…Among tubers, sweet potato and Dioscorea esculenta are the richest in total sugars, providing about 10 to 11 g of total sugars/100 g DW (Champagne et al., ). The content in total sugars of other tubers is generally low, at about 1.2% to 5.7% of DW (Lebot, Malapa, & Molisale, ). However, it greatly depends on the genotype (Champagne et al., ; Otegbayo, Asiedu, & Bokanga, ).…”

“…(h) Baah et al., ; Ezeocha & Ojimelukwe, ; Lebot et al., ; Njoh Ellong et al., ; Otegbayo et al., ; Wireko‐Manu et al., …”

“…Recent interest has dealt with the phenolic profile of tropical starchy fruits, roots, and tubers (Champagne, Hilbert, Legendre, & Lebot, ; Lebot et al., ; Passo Tsamo et al., ; Ramos‐Escudero, Santos‐Buelga, Perez‐Alonso, Yanez, & Duenas, ). There are wide inter‐ and intraspecific variations in phenolic profiles (Champagne et al., ; Lebot et al., ). As an example, it has been reported that most phenolic acids in sweet potato are chlorogenic, caffeic, and 3,5‐dicaffeoylquinic acids, whereas no phenolic acid was found in cocoyam.…”

“…However, most studies on the phenolic profile have dealt with HPLC or HP‐TLC techniques (Champagne et al., ; Lebot et al. ; Nadia et al., ). So, individual phenols have been tentatively identified.…”