**2.1 Botanical description**

*Cucurbitaceae* family is known to comprise some 101 accepted genera and the genus Momordica L. itself comprises of some 50 accepted species within the family [4]. *M. charantia* L. was known previously by several synonyms including the *Cucumis argyi* H. Lev., *Cucumis intermedius* M. Roem., *Momordica anthelmintica* Schumach. & Thonn., *Momordica charantia subsp. abbreviata* (Ser.) Greb., *Momordica charantia* var. *abbreviata* Ser., *Momordica charantia* f. *muricata* (Willd.)., *Momordica charantia* var. *muricata* (Willd.) Chakrav., *Momordica charantia* var. *pseudobalsamina* Griseb., *Momordica charantia* var. *zeylanica* Hitchc., *Momordica elegans* Salisb., *Momordica indica* L., *Momordica jagorana* K.Koch., *Momordica muricata* Willd., *Momordica papillosa* Peckolt ex Rosenthal., *Momordica roxburghiana* G. Don., *Momordica senegalensis* Lam., *Momordica thollonii* Cogn., *Momordica zeylanica* Mill. The botanical description of different parts of the plant demonstrated in **Table 1**. The taxonomic hierarchy of bitter melon within the plant kingdom is as follow:

**Kingdom:** Plantae **Subkingdom:** Viridiplantae **Superdivision:** Embryophyta **Division:** Tracheophyta **Subdivision:** Spermatophytina **Class:** Magnoliopsida **Super order:** Rosanae **Order:** Cucurbitales


### **Table 1.**

*Botanical description of* Momordica charantia *Linn.*

**Family:** Cucurbitaceae **Genus:** Momordica Linn. **Species:** *Momordica charantia* L.-balsampear

#### **2.2 Phytochemistry**

The main constituents of bitter melon are triterpenoids, saponins, protein, polysaccharides, steroid, alkaloid, lipid, and phenolic compounds. Several bioactive compounds of *M. charantia* L. have been recorded and the literature shown that these were responsible for various pharmacological effects as depicted in **Table 2** [5].

#### *2.2.1 Triterpenoids*

The most abundant phytochemical components of bitter melon fruits are the triterpenoids class of secondary metabolites, and are well-known for their bitterness


**Table 2.**

*Bioactive components of* Momordica charantia *Linn. And their pharmacological effects.*

and toxicity. These were divided in two types primarily the cucurbitane-type and to a less extent oleane type which may occur either in their glycosylated or aglycone forms. The sugar monomers as β-D-glucopyranosyl, β-D-allopyranosyl, β-Dxylopyranosyl occur in cucurbitane-type triterpenes either by their own as O-linked glycosides, or in different combinations as disaccharides or polysaccharides. The rare glycoside in these compounds was the 3-keto-glucoside [6]. An extremely large and certainly exhibited 193 number of cucurbitane-type triterpenes isolated from bitter melon having various pharmacological effects (**Table 3**) [7]. The fruits are predominance source of terpenoids with great deal of structural diversity but the leaves, stems and roots have also been shown to be good sources of these compounds [8].

Momordicosides A and B were isolated firstly from the seeds of bitter melon fruits; While, Momordicosides C, D and E were isolated as minor components of the seeds [9]. The study on the fruits of *M. charantia* L. further added a Momordicosides F1, F2, G, I, K and L as novel compounds in previous one [10]. The Momordicosides I and Momordicosides M along with other compounds have also been isolated from the fruits of bitter melon [11]. Further additions of Momordicosides M-O as a new compound were confirmed by chemical examination of the fresh fruits [12]. The Vietnamese origin dried fruits of *M. charantia* had shown existence of an auxiliary three pioneering Momordicosides U, V and W. The cucurbitane-type triterpenes which are known to be responsible for the bitterness of the leaves and vines of the *M. charantia* L. are Momordicines. The Momordicine IV and the malonyl derivative of Momordicine II, Momordicine V was readily available in the leaves of bitter melon. The isolation of Momordicines VI, VII, and VIII were first confirmed from the stems and leaves of bitter melon [13].

The Goyaglycosides-a, b, c, d, e, f, g, and -h were isolated from the fresh fruits of Japanese *M. charantia* L. A novel compound Goyaglycoside I was an additional triterpene isolated from the immature fruit of bitter melon [14]. The novel Cucurbitane-type triterpene called karavilagenins A-C and five new triterpene glycosides called karavilosides I-V were isolated from the dried fruit of *M. charantia* L. [15]. The three novel compounds that they names charantosides A, B and C were obtained from fruits of bitter melon. The methanol extracts of the fruits of Japanese *M. charantia* L. shown charantosides I, II, III-VI, VII and VIII, however charantoside IX and X were other novel compounds reported by the studies [16].

Another group of interesting triterpenoids are those known by their trivial names kuguacins. Kuguacins A-E and Kuguacins F-S were isolated from the roots and the leaves of bitter melon plant respectively [17]. Kuguacins II-VI was novel compounds isolated together with various other known compounds from the fruit of *M. charantia* L. From the aqueous ethanolic extracts of fresh fruits isolated eight novel cucurbitane-type glycosides that they named kuguasaponins A-H. The ethanolic extract of fruits of *M. charantia* L. identified 15 cucurbitane-type triterpene glycosides including 4 new compounds, kuguaosides A-D [18].

#### *2.2.2 Flavonoids and phenolic compounds*

A number of phenolic compounds with many biological activities have been isolated from bitter melon including, coumaric, caffeic, and ferulic acids as well as the caffeic acid ester, chlorogenic acid, Benzoic, gallic and gentisic acid. The major flavonoids and phenolic acids in the dried leaves of bitter melon were also analyzed and found to be rutin, gentisic acid and coumaric acid [19]. While the phenolic acids and flavonoids as well as their glycosides can be readily extracted by water, their non-polar derivatives may be present in the oil components of the plant.






#### **Table 3.**

*Pharmacological effects of cucurbitane type of triterpenoids of* Momordica charantia*.*

#### *2.2.3 Other components*

Other than the bioactive compounds, unsaturated fatty acids, alkaloids, amino acids minerals and vitamins are also present in bitter melon. The extracts of bitter melon shows nine kinds of unsaturated fatty. It has also been demonstrated that 12, 13 and 12 carbon fatty acids are found in young, mature, and senescent leaves of *M. charantia* L. representing 87.3%, 95.25%, and 83.11% of the total fatty acids respectively. The contents of total amino acids and the free amino acids of *M. charantia* L. were 11.99% and 2.36% as determined by acid hydrolysis and amino acid analysis. In addition, bitter melon is a natural source of vitamins; ascorbic acid was detected in the range of 440–780 mg in the fruit fraction. Vicine is an alkaloidal agent that has been isolated from the seeds of bitter melon, which is responsible for hypoglycaemic activity [20].
