Effect of Spice form and Extraction Period on Total Phenolic Content of Selected Ugandan Spices

Abstract

Introduction: Spice consumption is one of the globally recognized healthy nutritional practices. Most spices contain phenolic compounds that may prevent or prolong the onset of non-communicable diseases. The harvesting, processing and preparation procedures of such spices may influence the phenolic amount extracted and eventual biological availability. Literature about how extraction period and spice form affects total phenolic content yield in water infusions is scanty. Aim: This study determined the effect of spice form and length of extraction time on the total phenolic content (TPC) yield of the selected Ugandan spices infused in water. Methods: Samples of Ocimum gratissimum, Allium sativum, Cymbopogon citratus and Zingiber officinale, were collected in triplicates from Kanungu, Bushenyi and Lugazi Districts, in Uganda. Fresh and dry samples of these spices were infused in hot water for four minutes and 40 minutes and sieved with Whatman paper, No. 1. Phenolic content was measured with a spectrophotometer at Makerere University, Biochemistry Department, following Folin-ciocalteu method, using gallic acid as the reference standard. Results were analyzed using GraphPad Prism 8.0.1 software. Results: Higher TPC yield was generally observed in dry samples compared to the flesh ones and 40-minute extracts of both fresh and dry samples also had higher TPC content compared to the four minutes ones. The highest TPC yield was observed in Cymbopogon citratus (12.21±0.75 mg GAE/g) among the dry samples and Ocimum gratissimum (10.02±2.45 mg GAE/g) among the fresh samples, extracted for 40 minutes. Conclusion: Longer extraction time and sample dryness maximize TPC yield.  Ocimum gratissimum and Cymbopogon citratus may benefit consumers by improving their antioxidant status.