Antioxidant and Antiproliferative Activities of Several Garlic Forms

It is hypothesized that garlic, Allium sativum, might protect against oxidative stress that causes damage to cells and tissues leading to the development of various health conditions including cancer. However, it is not known whether garlic's potential anticancer benefits differ by form of garlic consumed. This study aimed to quantify and compare the in vitro antioxidant and antiproliferative activity of several garlic forms in water and alcohol extracts including fresh garlic, fresh garlic set aside, heated garlic, heated garlic set aside, garlic powder, black garlic, two commercially available garlic supplements. Antioxidant activity of different garlic forms were measured using three assays: DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) assay, superoxide assay, and hydroxyl assay. In vitro effects of garlic extracts were investigated against the most common lung cancer subtypes: H520, H1975, and A549 cell lines using the sulforhodamine B (SRB) assay. Among free radical scavenging assays, Garlicin®, a commercially available supplement, displayed high antioxidant activity in water and alcohol extracts (DPPH assay: 2.02 mg AAE (mg ascorbic acid equivalent)/g garlic and 3.53 mg AAE/g garlic, respectively; superoxide assay: 6.73 mg AAE/g garlic and 7.13 mg AAE/g garlic, respectively). In the hydroxyl assay, water extract of fresh garlic crushed and set aside for 10 min showed the highest antioxidant activity. Garlicin® alcohol extract and fresh garlic water extracts strongly inhibited the proliferation of H1975, A549 and H520 cells. Other forms of garlic including garlic powder and black garlic exhibited low antioxidant and antiproliferative activity. Our results demonstrate that the preparation and processing methods of garlic may lead to different antioxidant benefits.

Abstract 1609: Association between antioxidant levels and inhibition of lung cancer cell proliferation by various garlic extracts

Introduction:

Garlic is rich in organosulfur compounds that have potential chemopreventive properties. It contains a wide range of potent antioxidant compounds, which contribute by both radical scavenging activity and enhancing activity of enzymes. We aimed to investigate the antioxidant and antiproliferative activity of different garlic forms.

Methods:

Different types of garlic were obtained from a local Wegmans market in Buffalo, NY. Aqueous and methanol extracts of seven garlic forms including: raw garlic, raw garlic set aside for 10 minutes, garlic powder, cooked garlic, black garlic, and two garlic supplements (Garlicin and Kyolic) were investigated for their antioxidant and antiproliferative activity. Antioxidant activity was evaluated utilizing the 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) assay. The antioxidant activity of each sample was calculated in terms of gram equivalents of Trolox (TE) per gram of sample. Sulforhodamine B (SRB) assays were conducted to assess the antiproliferative effects after 48h of treatment with the extracts in cell lines selected to represent common cancer histologic and molecular lung cancer subtypes. Two-fold dilution concentrations of garlic extract were prepared ranging from 0.08% to 2.5% and the 50% inhibitory concentration (IC50) was calculated from dose-response curves. Each measurement of one sample was conducted in triplicate in order to average the antioxidant and antiproliferative measure for each garlic sample.

Results:

Among the different garlic forms, Garlicin supplement presented the highest antioxidant activity in both water and methanol extracts, 2.58 ± 0.43 and 3.45 ± 0.60 μmol trolox/g dry weight, respectively. Black garlic showed the next highest antioxidant activity in water and methanol extracts, 1.36 ± 0.53 and 0.19 ± 0.019 μmol trolox/g dry weight, respectively. Among lung cancer cells, different forms of garlic and different extraction methods resulted in varied percent inhibition. Garlicin alcohol extracts and fresh garlic water extracts resulted in a significant decrease in cell growth in H1975 cells and H520 cells, while other garlic forms showed lower levels of inhibition. Garlicin alcohol extracts and fresh garlic water extracts had the lowest IC50 values in H1975 EGFR mutant cells, 0.54% and 0.17% respectively. The same extracts were also potent in H520 squamous cells, 0.55% and 0.32%, respectively.

Conclusions:

In conclusion, Garlicin supplements and black garlic showed promising antioxidant activity, while Garlicin supplements and fresh garlic showed potent antiproliferative effects among lung cancer cells. Our results also indicate that the antioxidant and antiproliferative activity of different garlic forms are affected by different preparation and extraction methods. Further studies are needed to better understand the bioactive compounds present in garlic.

Citation Format: Zeinab Farhat, Pamela Hershberger, Diana Aga, Tyler Scheving, Ajay Myneni, Lina Mu. Association between antioxidant levels and inhibition of lung cancer cell proliferation by various garlic extracts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1609.