Profiling of polyphenolics, nutrients and antioxidant potential of germplasm’s leaves from seven cultivars of Moringa oleifera Lam.

https://doi.org/10.1016/j.indcrop.2015.12.032Get rights and content

Highlights

  • Leaves of different moringa germplasm have distinct phenolic profile.

  • Phenolics concentration was dependent on the variety considered.

  • Kaempferol-diglc and 3-caffeoylquinic acid were the most abundant phenolics.

Abstract

This work compares the polyphenolics composition, antioxidant activity and contents of selected nutrients in the leaves from seven cultivars of Moringa oleifera (‘Tumu’, ‘Sunyaw’, ‘Kumasi’, ‘Techiman’, ‘China’, ‘Pakistan Black’, and ‘Pakistan White’) representing the variety in Pakistan. Both the non-enzymatic (DPPH free radical and linoleic acid peroxidation inhibition assays) and enzymatic (superoxide dismutase, peroxidase, and catalase activities) antioxidant capacity was appraised. Regarding the nutritional value, in terms of protein and minerals contents, minor differences were recorded among cultivars. HPLC-PDA-ESI-MSn analysis of the hydro-methanolic extracts of Moringa leaves revealed a wide range of phenolics, highlighting their content in kaempferol derivatives, caffeoylquinic acid, and feruloylquinic acid. The antioxidant capacity of the tested leaves was correlated with the individual phenolics composition in order to identify which compounds were responsible for this beneficial power. The varying (p < 0.05) concentration of phenolics together with the antioxidant capacity of the tested leaves established ‘Pakistan Black’ and ‘Techiman’ as the most nutritive cultivar among others to be grown in the local area. Moreover, these data support the relevance of genetic variability of Moringa for determining the aptitude as a source of beneficial phenolics and nutrients, allowing to identify the optima cultivars to be grown in southern Asia.

Introduction

Moringa oleifera L. is a member of the Moringaceae family, native to India and Pakistan, which grows naturally at moderate altitude. Currently, moringa plants are widely cultivated in the Middle East, Africa and Southern Asia as a multipurpose crop (Sánchez et al., 2006, Nouman et al., 2014a), using a production system characterized by high biomass yield and fast re-growth after pruning (Foidl et al., 2001). Moringa crops can produce approximately 580 t/ha of moringa fresh shoot biomass annually. However, this yield is strongly dependent on the season, the weather conditions, the cultivar considered, and on the application of fertilizers (Palada et al., 2007). Besides yield, the analysis of the nutritional composition of moringa biomass has allowed to describe an interesting and balanced content of crude protein (16.8%), carbohydrates (9.9%), starch (7.9%) and lipids (4.9%) (Foidl et al., 2001).

To date, moringa leaves are used by agro-food and biochemical industries as a food, fodder, biopesticide, green manure, natural coagulant for turbid water, and plant growth enhancer (Bennett et al., 2003, Anwar et al., 2007, Gidamis et al., 2003, Nouman et al., 2012, Nouman et al., 2014b). Since moringa leaves have been investigated as a valuable source of dietary proteins and essential amino acids, hence, over the last several years their use as an ingredient in livestock and humans nutrition has been encouraged (Amaglo et al., 2010). Besides their use as an ingredient for foods and feeds; an impressive range of intrinsic bioactive phytochemicals including glucosinolates, isothiocyanates, carotenoids, and phenolic compounds of moringa leaves, has allowed to envisage their potential applications as a functional food and nutraceutical health promoter (Bennett et al., 2003, Fahey, 2005, Anwar et al., 2007, Amaglo et al., 2010, Leone et al., 2015). However, to date the biological activity and medicinal functions of moringa extracts has been mainly supported by in vitro assays based upon their antioxidant capacity and bioactives profile (Anwar et al., 2007, Sultana et al., 2009).

Data available on phytochemical composition of moringa plants suggest that the polyphenolic content of moringa is closely dependent on the germplasm considered, maturity stage, and agro-climatic conditions (Anwar et al., 2006, Nouman et al., 2014a). In this connection, to the best of our knowledge, so far these data are limited to specific germplasm (mostly Ghanaian or Malaysian cultivars), which have been mainly evaluated for polyphenolic content and innovative applications by food/pharmaceutical industries (Freiberger et al., 1998, Bennett et al., 2003). Whilst no such evaluation has been performed regarding moringa leaves of Pakistan (Black and White) as well as Chinese and African cultivars including ‘Tumu’, ‘Sunyaw’, ‘Kumasi’, and ‘Techiman’.

To date the antioxidant capacity of moringa leaves was supported by non-enzymatic assays namely DPPHradical dot and linoleic acid peroxidation (LAP) assays. DPPHradical dot is a non-biological radical extensively used to test the antioxidant capacity of plant extracts (Gironés-Vilaplana et al., 2014), whilst LAP assay is based on the capacity to inhibit of the linoleic acid peroxidation of vegetal samples (Osawa and Namiki, 1981). Thus, the implementation of these two methods with assays devoted to evaluate the enzymatic antioxidant activity could provide a more complete information regarding the antioxidant properties of moringa leaves.

The aim of this work was to evaluate the selected nutrients (protein and minerals content) and polyphenolic composition as well as the enzymatic (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities) and non-enzymatic antioxidant capacity of hydro-methanolic extracts of moringa leaves from seven cultivars representing the cultivars most extensively grown in the region (‘Tumu’, ‘Sunyaw’, ‘Kumasi’, ‘Techiman’, ‘China’, ‘Pakistan Black’, and ‘Pakistan White’). This information is intended to be integrated with the nutritional evaluation of moringa leaves in order to identify the most valuable cultivars and guarantee the sustainability of moringa crop in Pakistan.

Section snippets

Reagents

All LC–MS grade solvents were obtained from J.T. Baker (Phillipsburg, NJ). Formic acid was purchased from Panreac (Barcelona, Spain). The standards quercetin-3-O-glucoside and 5-O-caffeoylquinic acid were from Sigma–Aldrich (Steinheim, Germany). Ultrapure water was produced using a Millipore water purification system.

Plant material and sample preparation

M. oleifera seeds of the cultivars ‘Tumu’, ‘Sunyaw’, ‘Kumasi’, ‘Techiman’, ‘China’, ‘Pakistan Black’ (black seeded moringa), and ‘Pakistan White’ (white seeded moringa) were

Phenolic compounds

The HPLC-PDA-ESI-MSn analysis of hydro-methanolic extracts of moringa leaves revealed a wide range of phenolic compounds, being flavonols the major class (Table 1). Moreover, hydroxycinnamic acids were also detected in the analysed samples. Some of these compounds were recently identified in moringa leaves (Bennett et al., 2003, Amaglo et al., 2010, Khartivasan et al., 2013). Thus, according to retention time, molecular masses, and fragmentation patterns twelve flavonols and five cinnamic acids

Conclusions

To date, only a limited number of studies dealing with the nutritional and phytochemical composition of M. oleifera and the biological activity of its leaves’ extracts are available. In this connection, the overall results obtained in the present work revealed crucial differences regarding the phenolic profile of Moringa leaves as well as on the content of total and individual phenolics (phenolic acids and flavonols) along with enzymatic and non-enzymatic antioxidant activities among seven M.

Acknowledgement

This work was supported by national funds from FCT—Portuguese Foundation for Science and Technology, under the project PEst-OE/AGR/UI4033.

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