Microwave Assisted Extraction of Total Phenolics from Two Native UAE Plants and Evaluation of their Antioxidant Activity

  • Samar Al Jitan

Student thesis: Master's Thesis

Abstract

Halophytes are salt tolerant plants that can survive and complete their life cycle under saline conditions. There is a growing interest in halophytes because they can be sustainably cultivated on marginal soils and irrigated using either brackish water or seawater; conditions that are not suitable for conventional crops. Like other plants, halophytes produce secondary metabolites, such as phenolic compounds, that are of great medicinal value. The main objective of this study is to use microwave assisted extraction to recover phenolics from two halophytes, Arthrocnemum macrostachyum and Tetraena mandavillei. The influence of extraction duration (30 and 60 sec), solvent to sample ratio (30 ml:1 g and 30 ml:1.5 g) and concentration of ethanol in the extraction solvent (25%, 50%, and 75%) on total phenolic content (TPC) and antioxidant activity were determined. In addition to that, absorbance spectroscopy techniques were used to qualitatively identify the constituents of extracts obtained under optimal extraction conditions. Results indicate that the extraction duration and solvent to sample ratio had no effect on TPC (expressed as mg Gallic Acid Equivalent (GAE)/g extract). However, the concentration of ethanol in the extraction solvent did affect the TPC. Specifically, as the ethanol concentration in the extraction solvent increased from 25% to 50% to 75% so did the TPC of the botanical extracts from 36 to 42 to 46 mg GAE/g dry extract for Arthrocnemum macrostachyum and 23 to 30 to 54 mg GAE/g dry extract for Tetraena mandavillei, respectively. Results also indicate that the antioxidant activity of both plant extracts was not affected by the extraction duration, the solvent to sample ratio or the concentration of ethanol in the extraction solvent. Specifically, the antioxidant activity of Arthrocnemum macrostachyum extracts obtained with 50% and 75% ethanol were similar (approximately 75%), and slightly higher than the antioxidant activity of extracts obtained with 25% ethanol (approximately 64%). The antioxidant activity of Tetraena mandavillei extracts obtained with 25%, 50% and 75% ethanol were all similar (approximately 86%). Finally, the visible and infrared absorbance spectral profiles of both plant extracts strongly suggest the presence of phenolic compounds.
Date of AwardMay 2017
Original languageAmerican English
SupervisorLina Yousef (Supervisor)

Keywords

  • Arthrocnemum macrostachyum
  • Tetraena mandavillei
  • Halophytes
  • Unconventional Crops
  • Salt Water Agriculture
  • Microwave Assisted Extraction
  • Phenolics
  • Antioxidants.

Cite this

'