Introduction
Curry leaf (Murraya koenigii), also known as curry patta, sweet neem, pokok kari (Daun kari), and temurui. It is a small and strong-smelling perennial shrub with white flowers, belonging to the Rutaceae family that represents more than 150 genera and 1600 species. Curry leaves have a slightly pungent, bitter, and feebly acidulous taste. Curry leaves plant including bark, root, leaves, fruits, and fruit pulps is a highly valued plant for its aroma and possess various biological activities thus useful in traditional Ayurveda medicine (1). Some of the curries leave benefits are as follows
Distribution
Curry leaf is widely used as a spice in India and other tropical countries such as Sri Lanka, Bangladesh, Indonesia, and other South Asian countries.
Main constituents in curry leaves
Curry leaves contain a rich amount of proteins, carbohydrates, fiber, minerals, carotene, nicotinic acid, Vitamin C, Vitamin A, calcium, and oxalic acid. It also contains carbazole alkaloids, glycosides, tannins, reducing sugars, flavonoids, and phenolic acids including gallic, cinnamic, tannic, caffeic, ferulic, chlorogenic, and vanillic acids. Whereas curry leaves essential oil to contain various bioactive compounds as follows (2, 3).
Main constituents of Curry leave oil
| Compound | Amounts |
| Oxygenated monoterpenes | 72.15% |
| Monoterpene hydrocarbons | 11.81% |
| Oxygenated sesquiterpenes | 10.48 % |
| Sesquiterpenes hydrocarbons | 03.12% |
| α-pinene | 4.5-71.5% |
| Sabinene | <0.05-66.1% |
| γ-terpinene | 0.2-7.4% |
| (E)-caryophyllene | 1.6-18.0% |
| β-pinene | <0.05-13.6% |
| terpinen-4-ol | 0.0-8.4% |
| limonene | 1.1-5.5% |
| α-terpinene | 0.0-4.5% |
| (E)-nerolidol | 0.0-4.1% |
| α-humulene | 0.6-3.5% |
| α-thujene | 0.0-2.5% |
| β-elemene | 0.2-2.4% |
| β-selinene | 0.2-2.3% |
| Myrcene | 0.5-2.1% |
Health benefits of curry leaves
1. Good as a preservative agent
Curry leaves in combination with drumstick and mint leave useful as natural preservatives to increase the shelf-life of meat products (4).
2. Protect against piroxicam induced side effects
Piroxicam is one type of non-steroidal anti-inflammatory drug (NSAID) taken by arthritic patients but shows some side effects like gastric damage (ulcer), oxidative stress, and so on. However, intake of curry leaf earlier before piroxicam drug which has a high amount of antioxidants thus protect against piroxicam induced side effects. Therefore curry leaves may useful in combination therapy or dietary management to arthritic patients using piroxicam (5).
3. Boost memory
Daily intake of curry leaves improves memory, reduces amnesia thus helps for the management of Alzheimer’s disease (6).
4. Wound healing properties
Curry leaves contain antimicrobial and anti-inflammatory activity which is responsible for reducing inflammation through antibacterial protection of wounds which further leads to increase angiogenesis (formation of new blood vessels) and collagen deposition thus repair wounds (7).
5. Anti-cancer properties of Curry leaves
It contains a high amount of polyphenols, terpenoids, koenimbin, and girinimbine, a carbazole alkaloid that inhibits the activity of the cancer cell proteasome. Also, induce apoptosis, suppress inflammation and enhance the sensitivity of tumor cells to chemotherapeutic agents (8). Therefore intake of curry leaves in daily diet decrease the recurrence of cancer and protects the body from different types of cancers such as breast cancer, human colon cancer, cervical cancer, and human prostate cancer (9).
6. Manage diabetes and related complications
Intake of curry leaves helps to decrease blood glucose level, total cholesterol, triglyceride, urine sugar level and increase HDL-cholesterol level. Therefore, curry leaves show a wonderful effect in bringing down the severity of diabetes (10).
Curry leaves consumption also prevents the progression of diabetic neuropathic pain and diabetic neuropathy with symptoms like double vision, drooping eyelids, or weakness, and atrophy of the muscles. It helps in preventing nerve damage or control the symptomatic pain along with decrease the glycemic level (11).
Moreover daily oral administration of curry leaves increases the levels of plasma antioxidant capacity and decreases serum urea and creatinine levels thus curry leaves are helpful to treat diabetes-induced liver and kidney damage (12).
7. Anti-obesity properties
Curry leaves are a good source of carbazole alkaloids which show wonderful effects by a reduction in body weight gain therefore curry leaves consumption helps to prevent obesity (13).
8. Anti-inflammatory and analgesic properties of Curry leaves
It is a good source of alkaloids, triterpenoids, and flavonoids which are beneficial to reduce inflammation and relief from pain by blocking the sensation of pain by sensory neurons (14, 15).
9. Boost immunity
Curry leaves have the ability to remove harmful radicals from the body and increase immunity against various diseases thus curry leaves act as an immunomodulatory agent which stimulates immunity and degrade foreign particle in the body (16).
10. Antibacterial, mosquitocidal and antioxidant properties
Curry leaves extract is effective against Streptococcus mutans, Lactobacillus acidophilus, Mycobacterium smegmatisand Mycobacterium bovis that cause mycobacterial infection (17).
Curry leaves essential oil to contain linalool, elemol, geranyl acetate, myrcene, allo-Ocimene, and α-terpinene as well as carbazole alkaloids (mahanine and mahanimbicine). Which fights against different pathogens such as Staphylococcus aureus, S. pyogenes , Corynebacterium tuberculosis, Pseudomonas aeruginosa, Klebsiella pneumonia, Escherchia coli, Streptococcus pneumoniae and Enterobacter aerogenes and protect from different diseases (18).
Curry plant roots also contain carbohydrates, alkaloids, steroids, and flavonoids as well as carbazole alkaloids which show antibacterial and antifungal activity against Staphylococcus aureus, Micrococcus luteus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger (19).
Furthermore, carbazole alkaloids such a mahanimbine, murrayanol, and mahanine found in curry leaves show mosquitocidal properties thus useful as a mosquito repellent (20).
11. Presence of Antioxidants in Curry leaves
It contains high levels of phenolic acids (especially gallic acid) and flavonoids (especially myricetin, epicatechin, and quercetin) which is a promising source of antioxidant compounds that may be responsible for its anticancer activity (21).
12. Treat gingivitis, dental caries, and periodontitis
Curry leaves containing mouthwash are effective for the reduction of plaque and gingival inflammation thus keeps oral healthy (22).
Furthermore, a combination of leaves of curry, gum arabic tree, guava, and Eucalyptus herbal extracts fight against Streptococcus sanguisand Streptococcus salivarius and may use as antiplaque and anticaries agents to keep oral healthy (23).
13. Anti-anxiety and Anti-depressant properties of Curry leaves
Bioactive compounds in the leaf are effective to suppress oxidative stress which causes neurobehavioral disorders including anxiety and depression. Therefore curry leaves show a favorable effect for the treatment of anxiety and depression due to their sedative effects (24).
14. Treat Dyskinesia
Dyskinesia is one type of uncontrolled muscle movement due to an effect in the nervous system and causes by oxidative stress however intake of curry leaves which possess carbazole (alkaloids) that restore the levels of protective antioxidant enzymes and prevent abnormal oral movements (25).
Side effect of curry leaves
A research study suggested that intake of curry leaves do not cause any harmful effect on liver and kidney functions as well as food efficiency ratio (FER), red blood cell count (RBC), white blood cells (WBC), total count, differential counts or on the levels of blood constituents, like serum electrolytes, blood urea, hemoglobin and other parameters (26).