**9.5 Helichondrin B**

A complex polyether derived from the marine animals such as sponges, tunicates and their various predators. Compounds such as palytoxin, maitotoxin and halichondrins, because of their potential even very small quantities of these compounds could aid valuable commercial sense. Halichondrins was first isolated from the Japanese sponge *Halichondrin okadai* (Uemura). Halichondrin B and several natural analogs were subsequently been derived from various sponges such as, *Lissodendoryx* species, *Phakellia carteri* and *Axinella* species, thus it strongly suggest that this type may be constructed by an ascidian associated microorganism. A number of studies reported their cell toxicity, and it was found that halichondrins are tubulin inhibitors, noncompatitively binding to the vinca binding site and causing a charateristics G2-M cell cycle arrest by concomitant disruption of the mitotic spindle. *Dysidea herbacea*, a sponge and its symbiotic cyanobacterium *Oscillatoria spongellae*. These cyanobacterial cells are known to contain a series of highly distinctive chlorinated peptides, which has strong structural precedence in metabolites isolated from the free-living cyanobacterium *Lyngbya majusculea*. However a similar peptide from tunicate *Lissoclinum patella*, harbors an abundance of cyanobacterium *Prochloron* species which produces a series of distinctive cyclic peptides, associated with both cyanobacterial and tunicate cells. Palytoxin and maitotoxin are both available as research biochemicals [85].

#### **9.6 C-Phycocyanin**

A blue green pigment-protein complex isolated from the marine cyanobacteria *Agmenellum quadruplicatum, Mastigoclaudus laminosus*. This pigment appeared to be an activator of pro-apoptotic gene and also the down regulator of anti-apoptotic gene expressions [86]. Its activity of apoptosis on HeLa cell lines in-vitro, resulted from the transduction of apoptosis signals. These apoptosis further leads to the path of cell shrinkage, membrane bebbing, nuclear condensation and DNA fragment known to be observed from A549 and HT29 treated with C-phycocyanin.

#### **10. Conclusion**

However, a handful of antimicrobial peptides have found to be approved today for clinical use as anti-infectives. Cyclic peptides such as gramicidins and

#### *Insights on Antimicrobial Peptides*

polymyxins are well characterized. Gramicidins are used in treating infections such as infection of the surface wounds as well as the infections of nasal, ocular and throat infections. On the other hand polymyxins are used for treating eye infections prior to local administration and for selective decontamination of the digestive tract and also for systemic infections caused by drug-resistant gram-negative pathogens. Daptomycin, a cyclic antimicrobial peptides in clinical practice to treat skin complications and skin-structure infections caused by Gram-positive bacteria mostly, *Staphylococcus aureus*. Omiganan, a 12 amino acid analog of indolicidin, has been incorporated in the local treatment of Catheter related infections, atopic dermatitis, genital warts, acne vulgaris. Pexiganan, a 22 amino acid analog being evaluated in the Phase III clinical trials for the treatment of mild diabetic foot ulcers, burns and decubitus ulcers. PXL01, iron-binding lactoferritin present in milk and mucosal secretions, evaluated in phase II clinical trials for treating post-operative adhesions in patients undergoing flexor tendon repair surgery of the hands [87].
