Quality control and in vitro antioxidant potential of Coriandrum sativum Linn.

BACKGROUND: Coriandrum sativum Linn., commonly known as coriander, is a well-known spice and drug in India. It has various health-related benefits and used in various Unani formulations. In this present study, quality assessment of coriander fruits was carried out by studying anatomical characters, physicochemical tests, and chemoprofiling using high performance thin layer chromatography (HPTLC) and gas chromatography-mass spectroscopy (GC-MS) along with in vitro antioxidant potential.
MATERIALS AND METHODS: Standardization was carried out as per the pharmacopeial guidelines. Estimation of heavy metals, pesticides, and aflatoxins was carried out to ascertain the presence of any contaminant in the sample. Chemoprofiling was achieved by thin layer chromatography (TLC) by optimizing the mobile phase for different extracts. The most of the pharmacological activities of coriander are based on volatile oil constituents. Hence, GC-MS profiling was also carried out using hexane-soluble fraction of hydro-alcoholic extract. The total phenolic contents and in vitro antioxidant efficacy were determined using previously established methods.
RESULTS: The quality control and anatomical studies were very valuable for the identification whereas good antioxidant potential was observed when compared to ascorbic acid. The drug was found free of contaminant when analyzed for pesticides and aflatoxins whereas heavy metals were found under reported limits.
CONCLUSION: The work embodied in this present research can be utilized for the identification and the quality control of the coriander fruit.

Coriander (Coriandrum sativum Linn.) which belongs to Umbelliferae family is a well-known oldest spice and has been used in herbal formulations since long-time.[1] Coriander fruits are traditionally prescribed for fever, diarrhea, vomiting, and indigestion as carminative. It is also useful for vertigo and memory loss. The coriander oil is carminative and contains 65–70% of (+)-linalool (coriandrol), depending on the quality and the source. The drug was recently studied for hepatoprotective activity[2] and hypotensive effect.[3] The hypoglycemic and hypolipidemic potential of coriander extract has also been demonstrated in rats.[4] It was studied for its antioxidant efficacy.[56] The present work is based on the quality assessment and the antioxidant studies of coriander fruit. The present research will be helpful and can serve as an important tool for the quality assessment of the coriander.

Materials and Methods

Chemical and plant sample

The coriander sample was purchased from local market of New Delhi, India and the specimen (Ref. NISCAIR/RHMD/Consult/-2008-09/1149/181/02/01-08) authenticated by botanist Dr. H. B. Singh, Scientist F and Head Raw Material Herbarium and Museum, NISCAIR, New Delhi. The chemicals used in the analytical studies and solvents were purchased from Merck India. Standard catechin and ascorbic acid were purchased from Sigma-Aldrich (USA).

Morphology of coriander

The drug was evaluated for its physical appearance, shape, size, taste, color, and odor.

Microscopy of coriander

The samples of coriander fruits were fixed in 5.0 mL formalin +5.0 mL acetic acid +90 mL of 70% ethyl alcohol. After 24 h of fixing, the specimens were dehydrated with graded series of tertiary butyl alcohol. Infiltration of the specimen was carried out by gradual addition of paraffin wax (melting point 58–60°C) until tert-butyl acrylate solution attained supersaturation. The specimens were cast into paraffin blocks. The paraffin embedded specimens were sectioned with the help of rotary microtome. The sections were stained with toluidine blue, safranin, and iodine-potassium iodide. Different cell components were studied and measured. Microscopic descriptions of tissues were observed with micrographs using Nikon lab photo 2 microscopic unit (Nikon, Canada).[7]

Physicochemical evaluation

The physicochemical studies were carried out as mentioned in Indian Pharmacopeia (IP, 1996).[8] The different parameters such as determination of foreign matter, loss on drying, moisture content by Karl–Fischer titration, ash values with total ash, acid insoluble ash, and water soluble ash, pH of 1% and 10% solution of coriander powder, and extractive values were determined.

Chromatographic profiling

The high performance thin layer chromatography (HPTLC) fingerprints of petroleum ether, chloroform, and methanolic extracts of coriander were established by developing the solvent systems for their separation by thin layer chromatography. The gas chromatography-mass spectroscopy (GC-MS) analysis of hexane fraction of the hydro-alcoholic extract was also carried out.

Evaluation of contaminants

The heavy metal analysis for the presence of lead, cadmium, mercury, and arsenic was performed for the dried coriander powder. It was carried out using atomic absorption spectrometer. The AOAC method was used for the determination of aflatoxins (HPLC) and pesticides (GC-MS).[9]

Total phenolic content

Estimation of total phenolic content in coriander was carried out according to the Folin–Ciocalteu method using catechin as a standard phenolic constituent.[10] The absorbance was measured at 765 nm against blank, and concentration of phenolic contents in sample was calculated using regression equation of standard calibration curve.

In vitro antioxidant potential

1,1-diphenyl 2-picrylhyorazyl free radical scavenging method

The free radical scavenging capacity of coriander was determined using stable radical 1,1-diphenyl 2-picrylhyorazyl (DPPH) method.[11] The DPPH solution (0.004%, w/v) was prepared in 95% methanol. The extract and ascorbic acid (reference standard) in 95% methanol were tested in concentration of 5.0–100 μg/mL. Absorbance was read at 515 nm after 10 min against blank. Control samples were prepared using same volume without any extract and reference ascorbic acid. Percent inhibition of the DPPH free radical was measured using the following equation and IC50 value was determined using GraphPad Prism-5 (GraphPad Software, Inc., USA).

% Inhibition = ([A0−A1]/A0) ×100

Where A0 was the absorbance of the control (blank, without extract), and A1 was the absorbance of the extract or standard.

Nitric oxide free radical scavenging method

Nitric oxide (NO) radical scavenging activity of coriander was determined according to the methods reported.[11] The absorbance of the chromophore formed during the diazotization of nitrite with sulfanilamide and subsequent coupling with naphthylethylenediamine was measured at 540 nm after incubation of 30 min for standard ascorbic acid and sample extracts. The NO radicals scavenging activity of extract was calculated similarly to the DPPH method.

Results and Discussion

Morphology and microscopy of coriander fruit

The coriander fruit was yellowish brown to brown in color, globular, oval in shape, and 2–4 mm in diameter. It had aromatic odor and spicy characteristic taste. Mericarps of the fruit were usually joined by their margins forming a cremocarp often crowned by the remains of sepals and styles. The microscopic characters of coriander fruits are studied and presented in Figure 1.

Figure 1

TS of fruit showing pericarp, seed coat, and perisperm (a), Section stained with neutral red (b), cross section of the fruit showing pericarp and seed with perisperm (c), perisperm cells showing globoid and crystalloid (d), and perisperm cells viewed under polarized light showing brightly shining crystals (e-f). (Ep - epicarp; Ec - endocarp; Mc - mesocarp; IMc - inner mesocarp; OMc - outer mesocarp; Ps - perisperm; SMc - sclerotic mesocarp; SC - seed coat; Cr - crystals)

Different physicochemical parameters were carried out in triplicate [Table 1] with standard deviation. The obtained results were found under limits and comparable with pharmacopeial standards.[8]

Table 1

Summary of physicochemical parameters of coriander (n=3)

High performance thin layer chromatography

The satisfactory separation of constituents was obtained in solvent systems toluene:ethyl acetate (8:1, v/v) and toluene:ethyl acetate:formic acid (5:5:0.5, v/v/v) for petroleum ether and methanol extracts, respectively. The samples were applied, and chromatograms were developed. The petroleum ether gave good results after sprayed with anisaldehyde sulfuric acid as a visualizing agent and scanned at 450 nm for maximum absorbance of the peaks [Figure 2a]. The chromatogram of methanolic extract was scanned at wavelength of 254 nm, and results were found satisfactory [Figure 2b]. The HPTLC fingerprints of petroleum ether and methanol extracts showed the presence of 11 and 09 constituents, respectively.

Figure 2

Developed plates and high performance thin layer chromatography chromatograms of petroleum ether (a), and methanol (b) extracts of coriander

Gas chromatography-mass spectroscopy analysis

The GC-MS chromatogram showed that hexane fraction contains linalool as major constituent, whereas alpha pinene and eugenol are present in small amount [Figure 3].

Figure 3

Gas chromatography-mass spectroscopy chromatogram of hexane fraction of coriander extract

Test for heavy or toxic metal analysis

While using herbs as medication for various illnesses, one should be aware that apart from the pharmacological effect, they could turn out to be toxic because of the presence of heavy metals such as lead, cadmium, mercury, and other impurities. For these reasons, it is essential to control the level of contaminants in medicinal raw materials. The lead, cadmium, arsenic, and mercury were analyzed in coriander powder and found within the limits.

Aflatoxins

Aflatoxins are mycotoxins which are produced by some fungi of the genus Aspergillus that can grow on various foods, spices, and medicinal herbs. There are four major classes of aflatoxins, namely, B1, B2, G1, and G2. The aflatoxins B1 and G1 are more toxic in comparison to aflatoxins B2 and G2, which can cause acute structural and functional damage to the vital organs. Aflatoxins were analyzed using HPLC method in different samples of coriander. The chromatogram of mixed standard aflatoxins and sample showed that no aflatoxin is present in coriander sample.

Pesticides

The pesticide estimation was carried out using GC-MS, and after comparison of the chromatogram and retention time of standard 31 pesticides with the sample, it was observed that the test samples do not contain any pesticide.

Total phenolic contents

Recently, many reports suggest that phenolic compounds have an inhibitory effect on carcinogenesis and mutagenesis in humans and upon ingestion of high fruits and vegetables rich diet. The total phenolic content in the coriander was measured by Folin–Ciocalteu method and found to be 2.21% w/w.

In vitro antioxidant activity of coriander extract

1,1-diphenyl 2-picrylhyorazyl free radical scavenging activity

The coriander extract showed concentration-dependent antioxidant activity (5–100 μg/mL) by inhibiting DPPH radical with an IC50 value of 31.98 μg/mL whereas, IC50 value of ascorbic acid was found to be 16.41 μg/mL [Figure 4a]. It was found that the coriander extract possessed hydrogen donating capabilities about similar to ascorbic acid and acted as an antioxidant.

Figure 4

Log dose response curve of 1,1-diphenyl 2-picrylhyorazyl (a), and nitric oxide (b) free radical scavenging activity of coriander extract compared with ascorbic acid

Nitric oxide free radical scavenging activity

The results of NO scavenging activity showed that coriander extract has dose-dependent moderate activity between 5.0 μg/mL and 100 μg/mL with 63.87 μg/mL as IC50 value [Figure 4b] whereas IC50 value of ascorbic acid was found to be 15.90 μg/mL.

Conclusion

The present work has provided valuable information about identification, safety, and quality of coriander fruit. The in vitro antioxidant activity also found comparable to ascorbic acid, which may be a tool to check protecting efficacy of the drug. The work can be utilized for the quality assessment of the drug and herbal formulations containing coriander as an ingredient.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.