Introduction  

Shallot (Allium ascalonicum L. of Brebes) is one of the most frequently used horticultural commodities. Shallot is commonly used as a flavoring in food or as a cooking spice, and they have a variety of therapeutic effects [1]. Secondary metabolites in onion bulbs, such as tannins, saponins, essential oils, kaempferol, flavon glycosides, fluroglucin, dihydroalin, cycloalkene , methylalin, quercetin, polyphenols, sulfur, and flavonoids, can be used as traditional medicines.

Flavonoid is one of the compounds found in shallot with the highest content [2]. Flavonoids are pigments found in fruits, flowers, and leaves that contribute to the production of red, orange, blue, and purple colors. Flavonoids are a type of water-soluble polyphenol. The most important phytochemical in food is flavonoid bioactive, which have a wide range of biological benefits for humans [3].

Macerated extraction is a simple method of extracting flavonoid compounds from a sample based on the principle of immersing and stirring the sample in an appropriate solvent. When compared to other extraction methods, macerated extraction has the advantage of using more solvents [4]. This method is better because the extraction process is at room temperature to prevent flavonoid damage [5].

This study is about a qualitative test of Brebes shallot for secondary metabolites and flavonoid content, which was used as a preliminary investigation to determine the active substance content so that it could be used for more extensive research.

Materials and Methods

Tools and materials

Tools

The tools used for this research are glassware (Pyrex), oven (Memmert), rotary evaporator (bio base), maceration set, fractionation set, TLC, and UV lamp.

Materials

The materials used for this research are the Bima variety of shallot purchased from Brebes farmers in Central Java, Indonesia with GPS latitude location: -6° 52' 59.99" S and longitude location: 109° 02' 60.00" E., ethanol, ethyl acetate, acetic acid, quercetin, aqua dest, AlCl₃, methanol, acetic acid, a TLC plate, filter paper, and spirtus(Denatured alcohol). HCL₂N, Mayer's reagent, Bouchardat's reagent, Wegener's reagent, Sudan III, FeCl₃, concentrated hydrochloric acid, magnesium.

Work procedures

Extraction

A 200-gram sample was placed in the macerator container, and then 1:10 aqua dest was added. Maceration for 4 x 24 hours was followed by stirring for 5 minutes before being evaporated with a rotary evaporator at 70° to yield a thick extract.

Phytochemical screening

The presence of secondary metabolites in shallots was determined using phytochemical screening.

Identification of compound groups:

• Identification of alkaloid compounds

2 grams of the sample extract were added to a test tube and 5 ml of heated HCL2N were poured into it, After cooling, divided the mixture into three tubes and added Mayer’s reagent; if the alkaloids were positive, white precipitate forms. If positive, the second extract is added with Bouchardat’s reagent, which results in a brown-black color change. If positive, the third extract is added with Wagner’s reagent, which results in a brown precipitate.

• Identification of saponin compounds

If 1 gram of extract is placed in a test tube, 10 ml of hot water is added, allowed to cool, and then shaken vigorously for 10 seconds, and there is foam with a height of 1-10 cm in not less than 10 minutes, and 1 drop of HCL2N is added, the foam does not disappear, it is positive for saponins.

• Identification of tannin compounds

Add 1 gram of extract into a test tube, add 10 ml of hot water, then bring to a boil and add 3-4 drops of FeCl3 to the filtrate. If a blue-black color is formed, it is positive for tannin.

• Identification of essential oil compounds

Add the extract into the test tube, and then add Sudan III. If it is positive, the filtrate is orange.

• Identification of flavonoid compounds

Add the extract into a test tube, and then add 1 ml of 95% ethanol, 0.1 magnesium, and 10 drops of concentrated hydrochloric acid. If positive, a red color will be formed.

• Identification of terpenoids and steroids

In a test tube, 2 grams of the sample extract were combined with 2 ml of ethyl acetate and agitated. After drying, 2 drops of anhydrous acid and 1 drop of concentrated sulfuric acid were added to the ethyl acetate layer, which was put on a drip plate. If a red or yellow hue appears, it indicates the presence of terpenoids; if a green color appears, it indicates the presence of steroids.

Results and Discussion

The School of Biological Science and Technology, Bandung Institute of Technology, Indonesia, was used to determine the identity of the shallot plant from Brebes, Central Java, Indonesia. The shallot from Brebes was identified as Allium Ascalonicum L., a part of the Alliaceae family.

Using ethanol and ethyl acetate as solvents, extraction and fractionation results were obtained. In the maceration and fractionation processes, the solvent used is determined by the desired target compound. Non-polar solvents dissolve non-polar compounds, while polar solvents dissolve polar components. This is following the "like dissolves like" principle of dissolving a substance. A solvent's polarity can be determined using its chemical properties, namely the dielectric constant. The dielectric constant is a measurement of a solvent's polarity. Insolvents with a high dielectric constant, more polar compounds will dissolve [6].

Results of identification of secondary metabolic compounds

A small sample of shallot and a simple procedure wasused to conduct phytochemical screening to determine whether secondary metabolites are present. The results of qualitative compound identification based on observations can be seen in Table 1 and Table 2 below.