Evaluation of antioxidant activity, total phenols and phenolic compounds in thyme (Thymus vulgaris L.), sage (Salvia officinalis L.), and marjoram (Origanum majorana L.) extracts

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Abstract

The antioxidant properties and total phenolic of different extracting solvents of thyme, sage, and marjoram were examined using the stable 2,2-diphenyl-1-picrylhydrazyl-hydrate (DPPHradical dot) free radical scavenging method and Folin–Ciocalteu method, respectively. Methanol exhibited the highest extraction ability for such phenolic compound, where the total phenols were 8.10, 5.95, and 5.20 (mg gallic acid equivalent/g dry weight) for thyme, sage, and marjoram, respectively and also exhibited the strongest antioxidant capacity. On the basis of the results obtained, thyme, sage, and marjoram have a potential use as natural antioxidants due to their significant antioxidant activity. HPLC analysis of methanolic extract showed the presence of: rosmarenic acid, methyl rosmarenate, caffeic acid, cinnamic acid, chlorogenic acid and quinic acid as phenolic acids, besides some flavonoids such as ferulic acid, apigenin, luteolin and quercetin. The results demonstrated that thyme methanol extract possessed the best antioxidative activity, which were better than those of other plants, α-tocopherol and BHA.

Highlights

► The safety of synthetic antioxidants as food additives has received increasing attention. ► There is need components to act as antioxidants and to make food products safer. ► Detection of natural antioxidant sources for food use would be beneficial for healthy life. ► Antioxidant capacity of thyme, sage and marjoram extract was screened using DPPH assay. ► Thyme sage and marjoram exhibited stronger antioxidant activity than BHT and BHA.

Introduction

Herbs and spices have been used since antiquity for their flavoring qualities, and also, for their preservative and medicinal properties. Their extracts had been used in times BC in the Middle East to cure various disorders, spasmodic gastric-intestinal complaints, cough, bronchitis, laryngitis, tonsillitis and acting as carminative and diuretic agents. Topical applications of their preparations were used in the treatment of wounds, disorders of oral cavity and in oral hygiene.

For food uses, they are still employed to flavor meats, sausages, salads and soups (Novak et al., 2000).

Therefore, the demands for these plants are increasing in both industrialized and non-industrialized countries which lead to increasing their prices. Although Egypt is one of the countries having favorable conditions for the production of aromatic plants e.g. suitable environment and available low wages manpower (essential for service procedures, agriculture, collection and marketing) the cultivated area of these plants is not satisfactory because the farmers not interested in this kind of plants.

One of the principal causes of food quality deterioration is lipid peroxidation (Gordon, 1991). Lipid peroxidation results in formation of reactive oxygen species and free radicals; which are purportedly associated with carcinogenesis, mutagenesis, inflammation, DNA changes, aging, and cardiovascular diseases (Shahid et al., 2008, Siddhuraju and Becker, 2003).

The use of antioxidants in lipids and lipid-containing foods is one method to minimize rancidity, retard the formation of toxic oxidation products, maintain nutritional quality and increase the shelf life of food products (Pitchaon Maisuthisakul et al., 2007).

Synthetic antioxidants, such as butylated hydroxy anisole (BHA), butylated hydroxy toluene (BHT) and tert-butyl hydroquinone (TBHQ), are widely used in the food industry because they are effective and less expensive than natural antioxidants (Pin-Der et al., 1997). Their safety, however, has been questioned. TBHQ is banned in Japan and certain European countries (Shahidi, 1997) and BHA and BHT are reported to be carcinogenic (Ito et al., 1982). Hence, research for a safer and effective natural antioxidant is underway and several natural sources are being examined.

Antioxidants such as flavonoids, tannins, coumarins, curcumanoids, xanthons, phenolics, lignans and terpenoids are found in various plant products (such as fruits, leaves, seeds, and oils) (Jeong et al., 2004). For this reason, there is a growing interest in separating these plant antioxidants and using them as natural antioxidants. Different solvent systems have been used for the extraction of polyphenols from plant material (Pinelo et al., 2004). Extraction yield is dependent on the solvent and the method of extraction (Goli et al., 2004).

Water and aqueous mixtures of ethanol, methanol, and acetone are commonly used in plant extraction (Sun and Ho, 2005). Wang and Helliwell (2001) reported that aqueous ethanol was superior to methanol and acetone for extracting flavonoids from tea. However, in another work, water was found to be a better solvent, for extracting tea catechins, than 80% methanol or 70% ethanol (Khohar and Magnusdottir, 2002).

Among these herbs and spices, marjoram (Origanum majorana L.), of Lamiaceae family was known to the ancient Egyptians, Greeks and Romans (Tainter and Grenis, 1993). The Greeks felt it as a symbol of happiness and that if grown on the grave, the deceased would be eternally happy. Thyme (Thymus vulgaris L.) and sage (Salvia officinalis L.), also of the Lamiaceae family are the most important herbs from the aromatic and medicinal points of view (Stahl-Biskup and Saez, 2004).

Recently, spices have received attention also in their useful physiological functions and antimicrobial activity. More research is required on antioxidant activity of herbs and spices. The present paper deals with the chemistry and antioxidative behavior of oleoresins (extracted in ethanol, methanol, hexane and diethyl ether) of thyme, sage, marjoram.

Section snippets

Collection of plant materials

Leaves of thyme – Thymus vulgaris L. (Lamiaceae), sage – Salvia officinalis L. (Lamiaceae), marjoram – Origanum majorana L. (Lamiaceae) were randomly collected from Shambolia farm located at Fayoum area and stored in deep freeze at −20 °C until use.

Chemicals, solvents, reagents

2,2-Diphenyl-1-picrylhydrazyl (DPPHradical dot), butylated hydroxy anisole (BHA), tertiary-butylated hydroquinone (TBHQ), gallic acid, caffeic acid, chlorogenic acid, p-coumaric acid, ferulic acid, cinnamic acid, rosmarenic acid, hesperidin, quercetin, quinic

Extract yields and total phenols

The yield extracted from three aromatic plants by four solvents (methanol, ethanol, diethyl ether, and hexane) is represented in Table 1.

It could be noticed from the results that the highest extract yield was obtained by methanol extraction of all plant materials, followed by ethanol, diethyl ether and finally by hexane. The yields of both methanol and ethanol were: 24 and 14% for thyme; 23 and 18% for sage and 28 and 15% for marjoram. Hexane efficiency as a solvent was lower than the

Conclusion

As observed, extracts with higher antioxidant capacity also had higher polyphenol contents. It can be concluded that the extracts obtained using higher polarity solvents were more effective radical-scavengers than were those obtained using less polar solvents. Methanol showed better characteristics as a solvent for phenolic compounds than ethanol, but differences are not big, so for using in food industry ethanol is more adequate solvent. Furthermore, it is notable that the extracts from thyme

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