Phytochemical screening and assessment of health-related bioactivities of phenotic compounds from yacon [Smallanthus sonchifolius (Poepp. and Endl.) H. Robinson] leaves and tubers

Issue Date

8-2014

Abstract

Yacon [Smallanthus sonchifolius (Poeppig and Endlicher) H. Robinson], a tuber crop originally cultivated in the Andean region of South America, has been used as food and in traditional medicine by the native inhabitants for centuries. This study determined the nutritional value of yacon grown in Nueva Viscaya, characterized the phenolic constituents and evaluated their health-related bioactivities. By proximate analysis, a 100-gram sample of freeze-dried yacon tuber was found to contain low levels of protein (2.43 g), moderete level of fiber (4.47 g) and high level of carbohydrates (73.8 g). A 100-gram sample of fried yacon leaves contained high levels of protein (15.24 g) and fiber (5.67 g), and moderete level of lipids (2.81 g). Potassium comprised more than 50% of the total mineral content of yacon leaves and tuber, as determined by ICP-OES. Phytochemical screening showed the presence of phenolics, alkaloids, sesquiterpene lactones, terpenoids and triterpenoids; and absence of cyanogenic glycosides, salponins and glucosinolates in yacon leaves and tubers. The total phenolic contents of the tuber and leaf extracts, as estimated by the Folin-Ciocalteu method (in terms of mg GAE per 100 g sample and mg QE per 100 g sample) were: tuber methanol extract (164.2 ± 16.9 and 167.5 ± 15.0), leaf decoction extract (3,489.4 ± 129.9 and 3,484.7± 142.1) and leaf methanol extract (529.2 ± 52.4 and 214.8 ± 46.1). Descending two-dimensional paper chromatography, TLC and RP-HPLC analysis of the phenolic extracts and their products from acid- and base-hydrolysis showed that caffeic acid and its esters and derivatives were the major phenolic components. Qualification by RP-HPLC showed high levels (in terms of mg per 100 g sample) of a caffeic acid aster in the tuber extract (155.32 ± 0.67) and leaf decoction (186.72 ± 4.55), caffeic acid in the base-hydrolyzed leaf decoction (394.3 ± 0.7) and ferulic acid in the acid-hydrolyzed leaf decoction (43.32 ± 7.00). Results from chromatographic analyses corroborated by the isolation and identification of the following compounds by silica gel open column chromatography. ¹H-NMR spectroscopy and melting point determination: caffeic acid from leaf decoction base-hydrolyzed extract, and ferulic acid from leaf decoction acid-hydrolyzed extract. The phenolic extracts were found to have significant DPPH radical scavenging activity. Furthermore, the phenolic extracts exhibited significant anti-lipoperoxidative activity on rat liver microsomes comparable to a commercial supplement containing silymarin extract, which is recommended for hepatoprotection. Using the duck embryo CAM vascular irritation assay, the phenolic extracts, which found to possess an anti-inflammatory activity comparable to hydrocortisone.

Source or Periodical Title

Philippine Journal of Crop Science

ISSN

0115-463x

Volume

39

Issue

2

Page

1-11

Document Type

Article

Frequency

tri-quarterly

Physical Description

tables, graphs, charts

Language

English

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