Natural resins: chemical constituents and medicinal uses

Plants and their exudates are used worldwide for the treatment of several diseases and novel drugs continue to be developed through phytochemical research. There are more than 20,000 species of high vegetables, used in traditional medicines that are sources of potential new drugs. Following the modern medicine and drug research advancing, chemically synthesized drugs have replaced plants as the source of most medicinal agents in industrialized countries. However, in developing countries, the majority of the world’s population cannot afford pharmaceutical drugs and use their own plant based indigenous medicines. Several exudates from plants are well-known in folk medicine since ancient time, and they are today employed also for practical uses. Dragon’s blood is a deep red resin, which has been used as a famous traditional medicine since ancient times by many cultures. Dragon's blood is a non-specific name for red resinous exudations from quite different plant species endemic to various regions around the globe that belong to the genera Dracaena (Africa) and Daemonorops (South-East Asia), more rarely also to the genera Pterocarpus and Croton (both South America). Dracaena draco L. is known as the dragon’s blood tree, and it’s endemic to the Canary Islands and Morocco. Phytochemical studies of resins obtained from incisions of the trunk of D. draco, have led to the isolation of flavans, along with homoisoflavans, homoisoflavones, chalcones and dihydrochalcones. Dragon’s blood has been used for diverse medical applications in folk medicine and artistic uses. It has astringent effect and has been used as a hemostatic and antidiarrhetic drug. Frankincense, also known as Olibanum, is an old-known oleogum resin obtained from the bark of trees belonging to the genera Boswellia. There are 43 different reported species in India, Arabian Peninsula and North Africa. The importance of these plants is related to the use of extracts and essential oils of resin in traditional medicine like Ayurvedic and Chinese. Extracts from B. serrata resin are currently used in India for the treatment of rheumatic diseases and ulcerative colitis. Furthermore, extracts and essential oils of frankincense have been used as antiseptic agents in mouthwash, in the treatment of cough and asthma and as a fixative in perfumes, soaps, creams, lotions and detergents. In ancient Egypt the resin was used in mummification balms and unguents. Today frankincense is one of the most commonly used resins in aromatherapy. The biological activity of frankincense resins is due to the pentacyclic triterpenic acids, α- and β- boswellic acids and their derivatives, which showed a well documented anti-inflammatory and immunomodulatory activities. Manna is an exudate from the bark of Fraxinus trees (Oleaceae). Originally it was only collected from trees with damaged bark, but later in southern Italy and northern Sicily plantations were established for manna production, in which the bark is intentionally damaged for exudation and collection of manna. In July-August a vertical series of oblique incisions are made in the bark on alternate sides of the trunk. A glutinous liquid exudes from this cut, hardens as it oxidises in the air into a yellowish crystalline mass with a bittersweet taste, and is then harvested. Manna is still produced in Sicily, mainly in the Castelbuono and Pollina areas, from Fraxinus ornus and Fraxinus angustifolia trees. The main component of manna is mannitol; it also contains glucose, fructose, maltotriose, mannotetrose, minerals and some unknown constituents. Manna is a mild laxative and an excellent purgative, it is suitable in cases of digestive problems, in atonic or spastic constipation. It’s useful as expectorant, fluidifier, emollient and sedative in coughs; as a decongestant in chronic bronchitis, laryngitis and tonsillitis; in hypertonic solutions it acts as a dehydrating agent in the treatment of wounds and ulcers. It can be used as a sweetener in cases of diabetes as it does not affect glycemia levels or cause glycosuria; in addition it is also a cholagogue as it promotes the flow of the contents of the gall bladder and bile ducts and so stimulates bile production.