Scientific Research in School Volume 3 Issue 1 2021
Concentration of Allicin in Garlic Brianna Lollback Barker College The medicinal benefits of garlic have been extensively studied and attributed to the medicinally active thiosulfinate, allicin. This report outlines an investigation into whether temperature can be used to maximize the concentration of allicin in garlic, potentially maximising the medicinal benefits an individual can receive from consuming raw garlic. This investigation observed the effect of temperature on the concentration of allicin in raw garlic cloves, by using a spectrophotometric method that is sensitive enough to measure concentration of allicin in the micromolar range. The garlic cloves were subjected to different temperatures before the garlic was dehydrated and crushed into a fine powder and placed in solution. The data was recorded by first reacting the garlic extract with excess Lcysteine and then 5,5’-dithiobis-2-nitrobenzoic acid which measured the decrease in cysteine concentration. The results of the experiment found that temperature did not have a significant effect on the concentration of allicin measured when garlic cloves were stored over a period of four days. Literature review Garlic (Allium sativum L.) has been applied to culinary and medicinal purposes in modern and ancient practices (Peyman et al. 2013; Gaber et al., 2020; Azene, 2015). Garlic contains a rich source of organosulfur compounds responsible for its flavour and aroma as well as its health benefits (Oregon State University, 1985). Specifically, allicin, an organosulfur compound in garlic is responsible for the majority of the pharmacological activity of crushed raw garlic cloves (Lawson and Hunsaker, 2018), as it is the most biologically active compound in garlic (Rahman, 2007). Allicin, most commonly found in raw garlic, is known to reduce inflammation and offer antioxidant benefits (Bahare, 2019). Additionally, research has focused on allicin’s antimicrobial properties, which has found that allicin in its pure form exhibits antibacterial activity against a wide range of Gramnegative and Gram-positive bacteria, antifungal activity and antiparasitic activity against major human intestinal protozoan parasites such as Entamoeba histolytica and Giardia lamblia and antiviral activity (Ankri and Mirelman, 1999). Allicin is formed immediately in raw garlic as a self defence mechanism when the clove is damaged by worms, fungi, bacteria, or by physically crushing the clove (Leontiev et al. 2014). Allicin is produced by the precursor molecule, alliin (an amino acid) being converted into allicin by action of the alliinase enzyme (Figure 1) (Chhabria and Desai, 2018). The alliinase enzyme is located in the space between garlic cells, whilst alliin is located within the garlic cells themselves. This means that alliin and the alliinase enzyme can only
interact to form allicin once the cell walls of the garlic have ruptured (Janská et al., 2021).
Figure 1: Formation of allicin from alliin catalysed by the alliinase enzyme.
Allicin is known to be a highly unstable and volatile organosulfur compound due to the presence of the thiosulfinate functional group on the molecule (Abe, Hori and Myoda, 2019). This makes allicin heat sensitive, as it rapidly decomposes in the presence of air and water into an abundance of volatile thiosulfinate derivatives (mainly vinyl dithiines, ajoenes and allyl sulfides) (Figure 2) (Cheewinworasak et al., 2018). This is why there is an inability to ensure a certain abundance of allicin is present within a garlic clove. The effect of pH, concentration and light on the stability of allicin Research into the factors that influence the concentration of allicin have been vital in understanding the unstable nature of the allicin compound. A study by Wang et al. (2015) as well as a study by Lawson and Hughes (1992) investigated the influence of pH, concentration and light on the stability of allicin in garlic after crushing. Both
Science Extension Journal • 97
