General features: Delonix regia (DR) is a large tropical flowering plant belonging to the Fabaceae family of Delonix genus. Throughout the tropics around world, it is an ornamental / decorative tree often used for prettifying roads, highways, gardens, or meadows. In English, it is named as Royal poinciana, Phoenix flower, Flame of the forest, or even Flame tree. In India it is popularly known as Gulmohar (Hindi) meaning ‘flower stolen from peacock’. The term Gul means flower according to Persian language and ‘mor’ is short or colloquial version of mohar signifying peacock. In Bengal, the tree is adoringly named Krishnachura / কৃষ্ণচূড়া (Bengali) for its peacock feather appearance pointing to Hindus’ most romantic icon, Lord Krishna who himself decorates his crown using the feather. Another identical kind of the same family named Radhachura (রাধাচূড়া) is often seen to grow near it. This tree carries the name, Radha, (রাধা) after the name of Lord Krishna’s dearest darling love mate for her exquisite swanky look. The tree grows lesser sized flowers displaying yellowish or blonde appearance. Whereas the spectacular flamboyant appearance of DR displaying flaming scarlet hue pleases any human sense. Viewing its ostentatious splendor at the blooming season, poets across the world composed vast number of romantic poems. The plant represents a symbol of the romantic soul. The flowers appear in corymb having four large scarlet or orange-red petals, 3 inches in length. The fifth petal standing upright is skinny and long, dotted with yellowish- white. The pods are green and flaccid when young but turn deep brown at ripened stage. They are about 24 inches long and 2 inches wide holding small seeds weighing approximately 0.4 gm each. The leaves are doubly pinnate having feathery appearance with bright green color. Each leaf is 14 – 20 inches long holding about 20 – 40 pairs of leaflets divided into 10 – 20 pairs. The pollen grains have the size of ~ 20µM diameter. In tropical climate like in India flower blooms in monsoon season preferring hot and humid condition. The tree is not the native of India, presumably originated from the island of Madagascar. It finds its way to Kerala, the southernmost state of India although some believe that DR first arrived at Mumbai around 1840. From there it traveled to other states of India. It was discovered by an Austrian naturalist travelling in Madagascar around 1820. Later, the founder of Royal Society of Science and Arts, Sir Bojer introduced this plant in Mauritius. From there it traveled to many parts of the globe. In the US, it was introduced by a French man named, Phillipe de Longvillers de Poincy. The other name of tree, Royal Poinciana could be acquired after his name. DR also bears the name Kaalvarippoo or “flower of Calvary”. Christians believe that Jesus Christ was crucified near a Royal Poinciana tree on Mount Calvary. It is the blood of Christ that was splashed on the flowers turning them to vibrant red forever. The tree was introduced to Ayurveda by the then Indian Apothecaries to identify the medicinal activities. DR has impressive medicinal effects therefore it has been introduced as a folk medicinal source to combat rheumatism, inflammation, constipation, arthritis, hemiplegia, and leucorrhea. In addition to medicinal use, this large tree also provides substantial number of timbers to manufacture furniture and various construction and decorative needs.
Folk medicinal uses: For a long time, DR has been widely known for its traditional medical uses to treat various ailments. Below is the list for its actions of plant parts acting against numerous ailments.
| Plant parts | Medicinal uses |
| Bark | Febrifuge and antiperiodic. |
| Plant | Rheumatism, spasmogenic, cathartic, flatulence, emetic, CNS depressant, Anemia, and Fever. |
| Flowers | Anthelmintic, insecticidal, gynecological disorders, dysmenorrhea, febrifuge, Inflammation, and diarrhea. |
| Leaves | Bronchitis, pneumonia (particularly for infants), diabetic and gastric problems, body pain, and rheumatic joint pain. |
| Root | Abdominal pain |
Considering the overall perspectives, the most common Ayurvedic uses of DR are directed to act as antiinflammatory, antidiabetic, antiarthritic, antipyretic, cardioprotective also helping with indigestion and flatulence, purging parasites and worms out of digestive tract, antidiarrhea, anticancer, antimicrobial, and wound healing.
Phytochemicals: The tree synthesizes numerous phytochemicals of versatile nature in different plant parts. The bark contains Phyto-steroids, saponins, carotene, hydrocarbons, alkaloids, phytotoxins, and flavonoids. Flowers possess tannins, saponins, flavonoids, steroids, alkaloids, and carotenoids. Whereas the leaves produce lupeol, β – sitosterol, tannins, terpenoids, alkaloids, glycosides, carbohydrates, and sterols. The seeds contain copious amounts of saponins and fatty acids. The seed also contains 7 % fat, 45.2 % crude protein, and 39.5 % carbohydrate. In addition, it has neutral glycolipids, phospholipids, hydrocarbons, and several sterols. Regarding alkaloid, the identified and well characterized one is Cytisine, which is a heterocyclic compound having lactam ring bridged with a secondary amino compound. It is toxic by nature causing teratogenicity. Uniquely, the compound undergoes synthesis in plants of Fabaceae family. It is a nicotinic-acetylcholine receptor (nAChR) agonist thus often used as an aid for the cessation of smoking habit. The compound bears similarity concerning its molecular structure to nicotine. Cytisine / cytisinicline. Being a partial agonist to nAChR the compound has a short half-life (t1/2 ~ 4.8 hrs). It alleviates any urge to smoke cigarettes thereby lowering the severity of nicotine withdrawal symptoms thus subsequently diminishes the reward experience offered by nicotine from the smoking of cigarettes. Below are the major chemical constituents from various plant parts.
Major phytochemicals of Delonix regia
Other Phyto and their uses: The gum extracted from the bark contains galactomannans often used as matrix forming polymer due to its good swelling nature in aqueous media. Gum extracted from the seeds are used as a binder in preparing the Tylenol / Paracetamol tablets. The color extracted from flowers is used to dye fabrics, particularly silk. A single polypeptide chain serine protease inhibitor has been isolated which is noticed to have the excellent ability to inactivate trypsin (Ki ~ 21.9 nM) as well as human plasma kallikrein (Ki~ 5.25 nM).
Pharmacological role: The plant exerts numerous pharmacological actions by working as; 1) antioxidant, 2) hepatoprotective effect; 3) Anti-inflammatory and analgesic effect; 4) cytotoxic actions; 5) Hypoglycemic effect; 6) Gastroprotective effect; 7) Antiarthritic effect; 8) Wound healing role; 9) Antiemetic effect; 10) Antidiarrheal effect; 11) Antimalarial effect; 12) Antimicrobial effect; 13) Anthelmintic effect; 14) Larvicidal effect; 15)Antihemolytic effect; and 16) Diuretic effect.
Antioxidant effect – The antioxidant actions of leaves, flowers, and stem barks shows significant free radical scavenging ability which is due to its high phenolic contents. Among the plants, extract from flowers show the highest actions. The methanolic extract exhibits 81.9 % protection against brain lipid peroxidation whereas acetone extraction shows 80.8 %, followed by ethylacetate 79.4 % and aqueous extraction 77.8 %. The antioxidant potential of flowers relies on several constituents like carotenoids, anthocyanins, and other poly phenolic components.
Antiinflammatory and analgesic effect – The intraperitoneal administration of ethanolic extract of DR leaves (400 mg / Kg) to carrageenan induced rat paw edema and cotton pellet granuloma models shows significant antiinflammatory actions (48.1 % and 42.8 %) in comparison to standard indomethacin (10 mg / Kg) treated rats. The antiinflammatory compounds identified are flavonoids, triterpenoids, sterols, lupeol, and phenolic compounds. The extract of flowers and barks also show considerable antiinflammatory activities on identical experiments using carrageenan induced paw edema which is more effective than aspirin (300 mg / Kg). Studies on antinociception using acetic acid using hind paw experiments show that bark, leaves, and flower extracts possess potent analgesic effect when compared to Diclofenac (100 mg / Kg).
Hepatoprotective effect – The examination of serum enzyme levels along with histopathological analysis indicate that intraperitoneal administration of ethylacetate extract (100 mg / Kg) provide potent protective actions followed by ethanol and n-hexane extracts. The extract is enriched with flavonoids which is responsible for this physiologic effect. The extraction by ethanol which contains sterol (stigmasterol, β – sitosterol), flavonoids (quercitin, quercitin glycoside and rutin), and triterpene Ursolic acid) exerts robust protective role against CCl4 induced liver damages in rats which is better than silymarin.
Anticancer / cytotoxic effect – The extracts of stem bark, leaves, and flowers of DR can exert potent anticancer actions owing to its cytotoxic role on various cancer cells. The cytotoxicity is assayed either by following the lethality of brine shrimp bioassay by measuring percentage of lethality of brine shrimp, nauplii and subsequently determining the LC50 values which is often compared to vincristine sulfate (LC50 ~ 0.83 µg / ml). The bark extraction by CCl4 is quite identical to vincristine sulfate, LC50 ~ 0.83 µg / ml). The cytotoxicity of 70 % ethanolic extract of DR leaves on several cancer cell lines is measured by using MTT assay on breast cancer cells (MCF-7), cervix cancer cells (HeLa), few brain carcinoma and colon cancer cell lines and the results are, IC50 ~ 141.6, 223.7, 173.9, and 168.3 µg / ml. respectively. Tamoxifen has been used as a positive control. The ethanolic extract of flowers which is enriched with flavonoids, sterols, triterpenes (Ursolic acid), along with several aminoacids when applied to the human liver cancer cell line, HepG2 shows potent apoptotic or cytotoxic (IC50 ~ 0.55 µg / ml) effect.
Antidiabetic effect – The study is conducted on Alloxan induced diabetic rats using DR leaves extract (100 mg / Kg and 200 mg / Kg) administered orally. The extract significantly lowers blood glucose level with simultaneous reduction of total cholesterol, and serum triglyceride. The observed dosedependent effect is comparable to Glibenclamide / Glyburide. Interestingly, the reduction of blood glucose levels is also noticed among normal animals after two weeks of infusion of the extracts of leaf, flowers, and stem bark. The increased secretion of insulin from pancreatic β – cells is presumably the underlying cause.
Antimicrobial effect – The extracts of leaves, flowers, seeds, stem bark and root are evaluated for their antimicrobial actions using various strains of bacteria. The extracts are prepared by using CCl4, CH2Cl2, methanol, petether or simply the aqueous media. An overwhelming majority of the bacterial strains are seen to be significantly inhibited when tested both in vivo and in vitro.
Antimalarial activity – The extracts of fruit peels, leaves, barks, and flowers have shown considerable antimalarial effect when administered to mice infected with Plasmodium berghei using chloroquine as positive control. The inhibition is noticed to be significant from 87 – 76 %. The identified compounds are the mixture of alkaloids which are liable for antimalarial actions.
Miscellaneous effects –
- Anthelmintic activity – The aqueous extract of flower shows potent anthelmintic activity which is seen dosedependent. Active components might include tannins enable to interfere with the energy production by uncoupling oxidative phosphorylation.
- Antihemolytic effect – The methanolic extract of flower petals shows strong antihemolytic action against cumene hydroperoxide and H2O2 induced hemolysis. At 100 µg / ml concentration ~ 90 % inhibition has been observed.
- Diuretic effect – The effect has been evaluated by using methanolic extract of DR flowers (100 and 200 mg / Kg) keeping furosemide as positive control (20 mg / Kg) and normal saline as being negative control (25 ml / Kg). The increase of urine volume is seen being dose dependent.
- Anti-arthritic effect – The alcoholic extract of flowers shows powerful antiarthritic potential when used on animals having Freund’s incomplete adjuvant induced arthritis in laboratory rats, keeping Diclofenac as standard. The significant decrease in paw edema with subsequent increase in natural antioxidant enzyme levels (catalase, glutathione peroxidase, Glutathione – s- transferase) has been marked as an index of antiarthritic activity.
- Wound healing effect – The alcoholic extract of flowers shows considerable wound healing effect when tested on laboratory animals by using incision, excision, and dead space wound models. The identified components are possibly flavonoids.