Herbs are the nature’s gift to our mankind. Medicinal plants and their different parts such as flowers, buds, seeds, leaves, twigs, barks, woods, fruits, and root are used in herbal therapy. The World Health Organization (WHO) estimated almost 80 percent of the world population depends on herbal therapy to treat acute and chronic disorders. Recently it has been found that the young generation has also started to get connected to herbal therapy. Apart from typical medicinal plants like basil, ginkgo, there are other different spices like fennel, cumin, coriander which has medicinal properties. 
Herbal preparations in different dosage forms like tincture, powder, extract, tea, etc. are formulated in pharmaceutical manufacturing units. The different processes like polar and non-polar organic solvent extraction, steam distillation, hydro-distillation, vacuum distillation, supercritical fluid extraction, microwave-assisted extraction etc. are used to process and ensure that the bioactive components and phytochemicals status in these herbs and spices stay intact to provide best therapeutic value. 
The therapeutic value of medicinal plants is due to the presence of different phytochemicals, including polyphenols, flavonoids, glycosides, alkaloids, and tannins. Apart from their phytochemical constituents. Several nutrients such as vitamins, essential oils are also used in food industry and cosmetic preparations.  The different phytochemicals obtained from the medicinal plants and spices are as follows:
There are more than 8000 phenolic compounds present in different plant sources. They are having multiple functioning like protecting from UV rays, pathogens, and parasitic attacks. They also act as pigmenting agent for the plant. Phenolic compounds are potent antioxidants and act as a free radicals scavengers. All phenolic compounds do not have same bioavailability and therefore their efficacy varies. Phenolic acids, flavonoids, terpenes, tannins, stilbenes, and lignans are different phenolic compounds present in herbs. Some of these are discussed in detail:
They are divided into two groups. Gallic acid is a derivative of benzoic acid and coumaric, caffeic. Ferulic acid is a derivative of cinnamic acid. Apart from these two, hydroxycinnamic acid compounds and rosmarinic acid are the other phenolic acids that are abundantly found in herbs. All these phenolic acids possess antioxidant property with a variety of intensity .
Flavones, flavonols, flavanols, flavanones, isoflavones, and anthocyanins are different flavonoids present in plants with a variety of oxidation degree. In plants, the main source of flavonoids is glycosides and polymers, which are degraded in the gastrointestinal tract. These flavonoids are mainly effective to reduce the free radicals burden by providing antioxidant, chelating, and pro-oxidant activity. Medicinal plants mainly contain flavones like luteolin, apigenin, hispidulin, flavonol like quercetin, and kaempferol .
Myrcene, terpinenes, p-cimene, menthol, a-terpineol, carvone, thymol, carvacrol, etc. are different monoterpenes and the carnosic acid, rosmanol and epirosmanol are different diterpenes present in medicinal plants. They are essential components of essential oils and provides antioxidant properties .
Vitamin C and Vitamin E are two important antioxidants present in different herbs .
These phytochemicals are aromatic volatile oil with a strong odor. Terpenoids and phenylpropanoids are different metabolic products obtained from essential oil. In general, essential oils may have antibacterial, antiviral, antifungal, insecticidal, and herbicidal properties. They have antioxidant effect by acting as a free radical scavenger and reduce lipid peroxidation. They also have an anti-inflammatory effect by modulating pro-inflammatory gene expression.
Following are some commonly used spices and herbs, which possess different bioactive components and used to treat several diseases.
The scientific name of this herb is Rosmarinus officinalis, which belongs to Lamiaceae family. The different phytochemicals present in this herb are carnosic acid, carnosol, rosmarinic acid, rosmanol, isorosmanol, and epirosmanol. Among these different phytochemicals, rosmarinic acid is the major component present mainly in leaves, however, flowers, stems, and roots also have the phytochemicals. Rosemary herb is a well-known antioxidant due to the presence of these phytochemicals. This herb is used to prevent lipid oxidation and heme pigments degradation .
- The antidiabetic effect of Rosemary is due to its a-glucosidase enzyme inhibitory effect and also acts as a PPAR-g agonist.
- The anti-inflammatory effect of rosemary is due to the inhibition of iNOS protein expression.
- Rosemary inhibits the angiotensin-converting enzyme and provides the anti-hypertensive effect.
- This herb inhibits lipase activity and prevents lipid absorption which provides hypolipidemic effect .
The official name of sage is Salvia officinalis which belong to Lamiaceae family. The different phytochemicals that are present in this herb are carnosol, carnosic acid, rosmanol, rosmarinic acid and salvianolic acid L. Both, rosmarinic acid and salvianolic acid L provide potent antioxidant property to sage. Salvianolic acid L acts as a free radical scavenger .
- Sage inhibits a-amylase and a-glucosidase and increases serum insulin level. In addition, it also acts as PPAR-γ and provides the antidiabetic effect.
- It also reduces serum triglycerides and total cholesterol level, and improve lipid profile.
- Anti-inflammatory effect of sage is obtained by inhibiting inflammatory cytokine production and cyclooxygenase pathway .
The scientific name of this herb is Origanum vulgare. The rosmarinic acid is the most primary phytochemicals present in this herb; however other ingredients like caffeic acid, flavonoids, and derivatives of phenolic acids and Vitamin E are also present in this herb. Altogether, these phytochemicals provide potent antioxidant activities .
- Oregano can maintain glucose level in diabetes by increasing glucose uptake in the adipocytes and also antagonizes PPAR-γ due to its anti-oxidant property.
- It is also beneficial for cardiac health, as it reduces LDL and acts as an anti-inflammatory agent by decreasing Nitric Oxides (NO) synthesis .
The scientific name of this herb is Majorana hortensis. A wide variety of phytochemicals are present in this herb, like carnosic acid, and carnosol, followed by rosmarinic acid, caffeic acid, and flavonoids, luteolin-7-O glucoside, apigenin-7-O-glucoside and ursolic acid. The essential oil obtained from this herb contains terpinen-4-ol, γ-terpinene, and α-terpineol. Altogether these phytochemicals provide potent antioxidant activities .
- The presence of these phytochemicals also provide anti-diabetic effect and provide protection against diabetic nephropathy due to antioxidant property of marjoram.
- Marjoram has an anti-inflammatory effect, as it decreases NO production .
The scientific name of this herb is Thymus vulgaris. The different phytochemicals like thymol and carvacrol, rosmarinic acid, and flavonoids are present in this herb. Eugenol, thymol, and carvacrol are the different components of essential oil. Altogether, these phytochemicals provide potent antioxidant activities .
Basil (Ocimum basilicum)
The scientific name of this herb is Ocimum basilicum. Multiple antioxidant phytochemicals are present in basil, which include rosmarinic acid, caffeic acid, caffeoyl derivatives, and phenolic diterpenes etc. Researchers also found the presence of volatile oils, carotenoids, and vitamins, eugenol, tartaric acid, quinic acid, caffeoylquinic acid, β-carotene etc. to sustain the antioxidant effect of basil .
- Rosmarinic acid and catechin prevent different metabolic oxidative reaction and act as an anti-diabetic agent.
- The anti-inflammatory property of basil is due to its inhibitory effect against pro-inflammatory cytokines production.
- It also improves cardiac health by preventing the risk of atherosclerosis, as this herb lowers the total cholesterol and LDL level.
- It has antihypertensive action by improving endothelial functioning.
- This herb also improves kidney functioning .
Mint, peppermint, and spearmint
Mint, peppermint, and spearmint are the herbs of Mentha genus and scientifically known as M. officinalis (mint), M. piperita (peppermint), and M. spicata (spearmint), respectively. Eugenol, caffeic acid, rosmarinic acid, and vitamin E are most important phytochemicals present in all Mentha genus extracts and provide antioxidant properties. However, among all the Mentha genus extracts, M. piperita extract is a better antioxidant than other species .
Cumin has three varieties including, cumin (C. cyminum), black cumin (Nigella sativa), and bitter cumin (Cuminum nigrum). The, belong to Apiaceae family. The different phytochemicals like phenolic acids (chlorogenic acid), flavanoids, and coumarins are different phytochemicals present in this herbs. The essential oil is composed of different bioactive compounds like cumin aldehyde, cuminal, β-pinene, γ-terpinene, and safranal1. These ingredients give the antioxidant property to the cumin. Among the different varieties of cumin, bitter cumin has highest antioxidant property.
The anti-diabetic effect of curcumin is obtained by improving serum insulin level and also increase glucose tolerance. Eye health-related diabetes complication is also reduced with curcumin .
Foeniculum vulgare is the official name of fennel and belongs to Apiaceae family. Caffeoylquinic acid derivatives, hydroxycinnamic acid derivatives, flavonols and flavones, and their glycosides, coumarins are different phytochemicals present in fennel and provides antioxidant property. The essential oil obtained from fennel seeds contain trans-anethol, fenchone, estragole, and limonene. Apart from seeds, shoots, leaves, and steams also have antioxidant property .
• The potent antioxidant activity of fennel reduces the scope of diabetes-related complications.
• Fennel seed extract has anti-inflammatory and analgesic effect due to blockage of the arachidonic acid pathway.
• Fennel bulb extract has an antihyperlipidemic effect and reduces total cholesterol, triglycerides, LDL level and increases HDL. It also prevents lipid accumulation in the coronary artery and reduces the risk of CHD .
The rhizome of Curcuma longa belongs to Zingiberaceae family. Curcumin, bisdemethoxycurcumin, and demethoxycurcumin are three major curcuminoids (phenolic compounds) present in turmeric. Ferulic acid, p-coumaric acid, a-turmerone, and b-turmerone are other phytochemicals having antioxidant property. Turmeric has a wide range of health benefits1.
• The antioxidant property of turmeric is effective to treat a variety of cancers.
• The anti-inflammatory action of turmeric is due to its blocking action against inflammation triggering factor NF-κB and prevent many chronic conditions.
• Turmeric improves cardiac functioning by improving the endothelium lining of the blood vessels. In addition, antioxidant and anti-inflammatory actions of turmeric prevent heart diseases .
Botanical name of Ginkgo is Ginkgo biloba and belongs to Ginkgoaceae family. The different phytochemicals present in this herbs are catecholamine acid, coumarins, catechin hydrate, rutin, and quercetin. It also posses essential oil composed of cumin aldehyde, cuminal, and safranal1.Ginkgo is antioxidant and also provides following health benefits:
• Anti-aging property can reduce the incidence of short-term memory loss, depression, dementia, intermittent claudication, vascular fragility, poor circulation, impotence, and tinnitus.
• Improve circulatory effect can effective to treat and relieve the symptoms of peripheral occlusive arterial disease
• Analgesic effect of Ginko treats and prevent a migraine.
• Glaucoma can be treated with Ginko.
• Neurological beneficial effect of Ginko able to prevent stroke.
Apart from these, some of the common species like anise seeds, cardamom, and clove also have potent antioxidant activity due to the presence of various phytochemicals. Quercetin, luteolin, and apigenin glycosides are present in anise seeds; caffeic acid, p-coumaric acid, and protocatechuic acid are present in cardamom, eugenol is present in clove and cinnamaldehyde present in Ceylon cinnamon .
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- Maria Graça Miguel. Antioxidant and Anti-Inflammatory Activities of Essential Oils: A Short Review. Molecules 2010, 15, 9252-9287; doi:10.3390/molecules15129252
- Allyson Bower, Susan Marquez & Elvira Gonzalez de Mejia (2016)
The Health Benefits of Selected Culinary Herbs and Spices Found in the Traditional
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- Kartick Patra, Samarjit Jana, Deba Prasad Mandal,* & Shamee Bhattacharjee. Evaluation of the Antioxidant Activity of Extracts and Active Principles of Commonly Consumed Indian Spices. Journal of Environmental Pathology, Toxicology and Oncology, 35(4):299–315 (2016)