**4.1 Anticancer antimicrobial peptides**

Cancer cells are moderately anionic because of the negatively charged molecules present on their membrane-like phosphatidylserine, O-glycosylated mucins, sialylated gangliosides, and heparin sulfate [51]. In cancer cells, the asymmetry between the inner and outside membranes in terms of negatively charged phospholipids is lost, leads to an increase in negatively charged phosphatidylserine (PS) on the outer leaflet, which improves interactions with AMPs [52]. Due to these anionic molecules present on the cancer cells, electrostatic attraction occurs between cationic AMPs and anionic cancerous cells leading to membrane disruption through mechanisms like carpet or barrel-stave [53, 54].

Anticancer peptides also display anticancer activity through non-membrane targeting mechanisms (i) recruitment and activation of dendritic or macrophage cells to kill tumor cells (ii) obstructing angiogenesis to prevent tumor nutrition and metastasis (iii) inducing cancer cell necrosis or apoptosis (iv) activation of some functional proteins which interfere with tumor cell gene transcription and translation. It's worth noting that both net charge and hydrophobicity play key roles in anticancer activity optimization, and they are interdependent. For greater anticancer activity, maintaining a balance between net charge and hydrophobicity is crucial [11]. Examples of AMPs that exhibit anticancer activity are magainins and defensins [2].

#### **4.2 Antiviral antimicrobial peptides**

AMPs have been found to have inhibitory effects on a variety of DNA and RNA viruses, including HIV and influenza virus, herpes virus, and the hepatitis B virus.

AMPs have been discovered to have antiviral properties in various ways [22]. Antiviral peptides block viruses at various life cycle stages which include entry, attachment, penetration, uncoating, biosynthesis, assembly, and release. AMPs display antiviral mechanisms broadly through three ways: (i) hindering virus attachment and virus-cell membrane fusion; (ii) disrupting the virus envelope; and (iii) inhibition of virus replication by interacting with viral polymerase [12]. AMPs can potentially have an indirect antiviral effect, by altering the host immunological response. They can stimulate the synthesis of cytokines and chemokines, displaying both normal pro-inflammatory activity and triggering the infectioninduced inflammatory response. AMPs may also operate as a chemoattractant, attracting immune cells to the infection site and aiding viral clearance [55]. Examples of AMPs showing antiviral activity include α-defensins interfere with the ability of the human immunodeficiency virus (HIV) to multiply within CD4 cells by directly inactivating viral particles. Retrocyclin 2 is a synthetic θ-defensin, capable of preventing influenza virus infection. Human β-defensins can prevent HIV-1 replication [26].

#### **4.3 Antifungal antimicrobial peptides**

Antifungal antimicrobial peptides attack either intracellular components or cell walls, causing fungal cell membrane integrity to be disrupted and permeability to be altered due to pore creation in the membrane structure [12]. Antifungal peptides have several recognized mechanisms of action including, (i) direct membrane disruption, (ii) inhibition of cell wall formation, primarily of components like (1,3)- β- d-glucan or chitin, and (iii) interaction with fungal mitochondria [2]. A classic example of an AFP that inhibits 1,3- β-glucan synthase is the echinocandin family. This enzyme is crucial for fungi to maintain cell wall stability. The cell wall

is destabilized and the cells become vulnerable to osmotic pressure when the function of this enzyme is blocked. The β-glucan synthase enzyme is broadly found in *Aspergillus, Cryptococcus, Candida, and Pneumocystis* species. Inhibitors like nikkomycin and polyoxins are known to block chitin synthase in species like *C. albicans* [12].
