Phenolic Composition and Antimicrobial Activity of Different Emirati Date (Phoenix dactylifera L.) Pits: A Comparative Study.

M Iftikhar Hussain,Wameed Radeef,Ismail Saadoun,Abdallah Shanableh,Islam M Ahmady,Mohammad H Semreen,Muath Mousa,Muhammad Nasir Khan Khattak,Sameh S M Soliman,Nora Darwish

doi:10.3390/plants8110497

Abstract

The biochemical composition, secondary metabolites (phenolic compounds, flavonoids) and antimicrobial potential of different varieties of Emirati date (Phoenix dactylifera L.) pits were investigated. Total phenolic acids (TPC) and total flavonoid contents (TFC) of the different date pits were measured using a Folin–Ciocalteau reagent. Different organic solvents [(n-hexane; H2O: EtOH (1:1); ethyl acetate; acetone: Water (1:1); and methanol: Chloroform (1:1)] were compared to evaluate the phytotoxicity of Ajwa, Fard, Khalas, Khodari, Abu Maan, Lulu, and Mabroom date pits. The antimicrobial activity of the date pit extracts were evaluated by means of agar-well diffusion assay on Staphylococcus aureus (ATCC 29123), Escherichia coli (ATCC 25922) and Candida albicans (ATCC 66027). Minimum inhibitory concentrations (MICs) were measured following clinical laboratory standardization institute (CLSI) protocol. The biochemical analyses of date pits indicate that TPC were ranged from 7.80 mg of equivalent gallic acid⁄100 g dry weight in Ajwa to 4.65 mg in Mabroom. The TFC were ranged between 1.6–4.54 mg of equivalent catechin⁄100 g dry weight. Ajwa pit extract showed good quality traits (higher protein, lower ash content, and intermediate dietary fiber). The results indicate that the ethyl acetate extract of Khalas and Khodari inhibited S. aureus with an inhibition zone diameter of 20 mm and MIC of 10 mg/mL. Abu Mann pit extract inhibited the S. aureus and also decreased the population of E. coli. The diameter of inhibition zone was 15, 16, and 18 mm after treatment with Ajwa extracts, while the MICs were 7.5 and 5 mg/mL. The MeOH: CFM extract of Abu Mann and Ajwa was more potent against E. coli bacteria than any other extract. This work demonstrates that the Emirati date pits extract has antimicrobial (antibacterial, antifungal) potential and can be used as phytotoxic natural compounds.

Highlights

Date palm (Phoenix dactylifera L.), is a highly nutrient-rich fruit, originating from the ArabianPeninsula, North Africa, and the Middle East
The fruits of date palm varieties, Abu Maan, Fard, Khalas, Ajwa, Mabroom, Lulu, and Khodari were purchased from Al FOAH COMPANY, Al Saad, Al Ain, Abu Dhabi, United Arab Emirates (UAE)
There was a significant difference between moisture contents that ranged between 9.72–16.28%

Summary

Introduction

Date palm (Phoenix dactylifera L.), is a highly nutrient-rich fruit, originating from the ArabianPeninsula, North Africa, and the Middle East. Date fruit is a rich and cheap source of carbohydrates, proteins, amino acids, and minerals (selenium, potassium, calcium, magnesium, manganese, and iron), dietary fiber, vitamins, carotenoids, and fatty acids [2,3]. The biological and therapeutic potential of date flesh and pits demonstrate the presence of polyphenols and flavonoids in both plant tissues [4]. Dates are an important source of different phytochemicals such as flavonoids, phenolic acids, anthocyanins, tannins, and carotenoids [5,6]. Volatile compounds, flavonoids (apigenin, luteolin, and quercetin), phytosterols (β- sitosterol, iso fucosterol, stigmasterol, campesterol), and carotenoids (lutein, neoxanthin, β-carotene, violoxanthin, antheraxanthin) were reported in date fruits and pit extracts [7,8]. Different date varieties contained soluble phenolic compounds like hydroxybenzoates, hydroxycinnamates and flavonols [10]. The ripe stage of Khasab, Fard, and Khalas were reported to contain 20, 35, and

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Conclusion