Alkaloids | VINCA

Vinca

Synonyms- Catharanthus, Periwinkle, Sadabahar, Madagascar plant. 

Biological source

         It is a dried entire plant of Catharanthus roseus, it is also known as Vinca rosea, 

Family -Apocynaceae.

Geographical source-

         It is indigenous to Madagascar. It is cultivated in India, Europe, USA, Australia, Caribbean island, South Africa as an ornamental plant as well as for its medicinal properties.

Cultivation-

• Vinca grows all over the India but it is well grown in tropical and subtropical areas in South India and North Eastern states of India.
• Vinca grows in light sandy soil rich in humus and rainfall of about 100 cm is most suitable for propagation.  
• Vinca does not required much water or fertilizer but farm yard manure sometimes used.
• Fresh seeds are sown in nurseries or direct sowing is done for cultivation.
• For direct Sowing the seeds are mixed with 10 times quantity of sand and sown in monsoon in rows of 45 cm apart, about 2.5 kg of seeds per hectare is required.
• When the plants sufficiently grew up they are sown with a distance of about 30 cm is left between two plants.
• For nursery sowing seeds to be sown economically in February or March.
• When they achieve 6-7 cm height, they are transplanted  in open fields at 45-35 cm distance apart.
• About 74000 plants per hectare are necessary.

Collection and preparation

• Collection is done by live stripping at every 6 to 9 months after sowing.
• The stems are cut about 6 to 8 cm above the ground level after one year of growth and leaves, stems, and seeds are separated and air dried.
• For collection of roots, the fields are profusely irrigated and roots are dug out by ploughing, then roots are further washed, dried in Shade and packed in bales.
• Seeds are collected from mature fruits for next propagation.
• The yield of dried roots, stems and leaves for hectare in irrigated land is about 1 to 3 tones respectively.

The extraction and separation of alkaloids-

 

          The extraction is based on their separation into soluble and insoluble tartrates in other Solvents. Due to this vinblastine, vincristine and other weak bases are separated and then fractionated with the help of column chromatography by using Alumina as a adsorbent.

Tissue culture techniques also used for isolation of vinca dimeric indole alkaloids like catharanthine and ajmalicine, but not utilised for commercial uses.

Macroscopic character-

• Colour- leaves are green, roots are pale grey, flowers are violet pink-white or carmine-red in colour. 
• The odour - characteristic 
• Taste- bitter
• Vinca is an erect, pubescent herb, with branched tap-root. Leaves are simple, petiolate, ovate, or oblong, unicostate, reticulate, entire, brittle with acute apex and glossy appearance. 
• Flowers are bractate, pedicellate, complete, hermaphrodite, normally 2 - 3 cm in cymose axillary clusters.
• Fruits are follicles with several black seeds.

Microscopic character- 

• Upper surface shows presence of single layer of rectangular celled epidermis with unicellular covering trichomes.
• Palisade is made up of single layer beneath upper epidermis and contains compact elongated cells. 
• Spongy parenchyma is 5 - 8 layered with intercellular spaces. 
• Midrib shows presence of collenchyma below the upper epidermis and above the lower epidermis. 
• Xylem and phloem are present in the centre.
• Cruciferous stomata are present more frequently on lower epidermis. 
• Calcium oxalate crystals are absent.

Chemical constituent- 

• Vinca alkaloids are large number of indole alkaloids, about 20 dimeric indole-dihydroindole alkaloid possess oncolytic activity.
• Vincristine, vinblastine structureinblastine contains alkaloid part called catharanthine and dihydroindole alkaloid part called vindoline. 
• The other alkaloids present in vinca are ajmalicine, lochnerine serpentine and tetrahydroalstonine. 
• It requires about 500 kg crude drug to extract out 1 g of vincristine, because of its extreme low content, viz. 0.0002 per cent. This makes these alkaloids very costlier and hence, the efforts for their synthesis are under attempts. 

Uses-

• Vinca is used for the extraction of vincristine, vinblastine and ajmalicine. 
• vincristine sulphate is antineoplastic agent act by arresting mitosis at metaphase.
• It is also used in treatment of acute leukaemia of children, hodgkin’s disease in adults, reticulum cell sarcoma, lymphosarcoma, myosarcoma shown short remission.
• Vinblastine sulphate is used as antineoplastic agent which act by arresting mitosis at metaphase or by interfering with amino acid metabolis, suppresses immune response, mainly used in the treatment of hodgkin’s disease and other carcinomas.
• Vinca also exhibit hypotensive and antidiabetic actions.