Study on Antioxidant Activities of Soaps with Coffee Ground Extract and Soaps with Mixed Coffee Ground Extract and Mulberry Leaf Extract

Abstract

Background and Objectives: The objective of this research was to develop glycerin soap products containing Arabica coffee ground (Coffea arabica L.) extract, mulberry leaf (Morus alba L., c.v. Chiang Mai 60) extract, and coffee ground. Coffee ground contains phenolic compounds and caffeine, which exhibit antioxidant activity, helping to delay aging and reduce swelling and inflammation of the skin. Mulberry is a type of plant that is widely grown in Lopburi province. Mulberry leaves contain polyphenolic compounds, therefore exhibiting antioxidant activity.

Methodology: Coffee grounds were obtained from a coffee shop in Lopburi province. The coffee grounds were dried in a hot air oven at 80 °C for 10 hours. Extraction of coffee grounds was prepared by weighing 100 grams of coffee grounds and extracting with 500 mL of deionized water at temperature of 100 °C for 1 hour. After that, the extract was filtered through white cheesecloth and filter paper (Whatman no. 1). Mulberry leaves were obtained from mulberry farms grown in Lopburi province. The mulberry leaves were washed, air-dried, and then cut horizontally to a thickness of approximately 0.5 cm. Mulberry leaf extract was prepared by weighing 40 grams of mulberry leaves and extracting with 500 mL of deionized water at a temperature of 100 °C for 1 hour. Then, the extract was filtered with white cheesecloth and filter paper. A transparent glycerin soap base was used in this work. There are 8 formulas of soap, including control soap (formula S1), 3 formulas of soap with coffee ground extract (formula S2-S4), 1 formula of soap with coffee ground extract and mulberry leaf extract (formula S5), 2 formulas of soap containing coffee ground extract and coffee ground powder (Formula S6-S7), 1 formula of soap containing coffee ground extract, mulberry leaf extract, and coffee ground powder (S8). A soap was prepared by weighing 25 grams of glycerin soap base and melting the glycerin over low heat. After that, the prepared components were added. Then, the solution was stirred and poured into the oval silicone soap mold. Physical and chemical properties of soaps, including foreign matter, color values, erosion percentage, bubble volume, durability of the bubbles, and pH, were studied. Antioxidant activities of soaps were determined by the DPPH assay.

Main Results: Eight soap formulas with different ingredients were compared. The results indicated that all soaps had no foreign matter. The color values of soap with coffee ground extract, mulberry leaf extract, and coffee ground, as expressed in terms of L*, a*, and b*, were 13.81 ± 1.20 to 26.40 ± 0.97, 0.44 ± 0.13 to 1.36 ± 0.22, and 0.20 ± 0.24 to 4.76 ± 0.31, respectively. The pH values were 9.81 - 10.06. The erosion percentage, bubble volume, and durability of the bubbles were 14.83 ± 1.37 to 16.55 ± 1.45 %, 69.50 ± 1.50 to 73.00 ± 3.12 mL, and 66.00 ± 2.00 to 70.25 ± 2.65 mL, respectively. Antioxidant activities of soaps as determined by the DPPH assay were in the range of 1.66 ± 0.11 to 7.65 ± 0.02 ascorbic acid equivalent (AAE)/g soap. The results of the satisfaction assessment of the soap products obtained from a panel of 25 people were at a very satisfactory level.

Conclusions: All soap formulas developed had physical and chemical properties meeting the standards of bar soap product requirements. The developed soaps had higher antioxidant activities than the control soap. The coffee ground extract, coffee ground powder, or mulberry leaf extract added to soap increased the antioxidant activities of soap. It also allows for a variety of shades of soaps.

Practical Application: The developed soaps could serve as quality soap prototype products for a community. The soaps could also serve to increase the value of spent coffee grounds and local herbs.