Various proteins and peptides have ability to self-aggregate by disturbing their original tertiary functional structure under appropriate physiological conditions [[1], [2], [3], [4]]. These types of aggregation lead to formation of highly ordered, rigid and β-sheet enriched amyloid fibrils [5,6]. Deposition of fibrillar aggregates in different parts of our body are closely associated with a wide number of disorders including Alzheimer's, Parkinson's, Huntington's, familial amyloidosis and type-II diabetes [[7], [8], [9], [10], [11], [12], [13]].

Lysozyme, protective enzyme, have been identified in different types of plant, animal and microbes. There are conventionally three types of lysozyme i.e. i. Chicken/Hen type (also known as conventional type or c type) ii. Goose type (g type) iii. Invertebrate's type (i type). Some plant and microbial types have been also separated. Lysozyme can easily rapture bacterial cell wall by hydrolysing glycosidic linkage of peptidoglycan. For this reason it is endowed with natural antimicrobial action against different fungal, bacterial and viral pathogens [14].This enzyme is widely distributed in variety of body fluids and tissues in gastrointestinal tract, kidneys, liver, lymph nodes, spleen, skin, lachrymal and salivary glands [15]. As it has several enzymatic roles to play, its amyloidosis can lead to multi-organ disorders, haemorrhagic complications and different slow-moving life threatening diseases. As mentioned previously neurodegenerative disorders may also lead to autosomal dominant genetic diseases [8,9,[16], [17], [18]].

Lysozyme fibrillation process is a well-studied regular kinetic process [[19], [20], [21], [22], [23], [24]]. Formation of cross β sheet stable structure from α helical shape during fibrillation is monitored through different analytical approaches [5,19,25]. Lysozyme is popularly used as a model system for analysis of protein aggregation [25].

Human lysozyme has 130 amino acid residues with 59 % sequential homology to hen egg white lysozyme (HEWL). HEWL has stable tertiary structure with 129 amino acid residues having α helical, β sheet, loops & turns and some unordered structure composition under different conditions [[26], [27], [28]]. There are two types of natural inherent fluorescence active residues i.e. Tryptophan (Trp) and Tyrosine (Tyr) [28,29]. The active drug binding site of lysozyme is situated at its big hydrophobic crevice which is linked with α helix conformation [[30], [31], [32], [33]]. Lysozyme fibrils are more compatible with fibrillar β-rich structure and it can be stabilized by addition of salt, pH changes or any denaturants [34,35].

Different in-vitro and in-vivo studies have shown that several natural products and synthetic molecules including polyphenols, alkaloids, nanoparticles, dyes, ionic liquids etc. have therapeutic efficiency to inhibit fibrillation of lysozyme [[36], [37], [38], [39], [40], [41], [42], [43], [44], [45], [46], [47], [48], [49], [50], [51]]. Dozens of compounds having these types of antiamyloidogenic capability fail at different stages of clinical trials [52]. So searching for an efficient antifibrillar therapeutic is an important area of current research to fight against the neurodegenerative diseases.

Natural alkaloids are considered to be of potential antiamyloidogenic value with minimum cytotoxic effect [52].These types of alkaloids have well defined pharmacokinetics and pharmacodynamics with proteins and enzymes [[53], [54], [55], [56], [57]]. Some alkaloids like berberine, palmatine, coralyne, chelerythrine, sanguinarine etc. have conventional drug like static binding in physiological condition with estimated binding free energy ranging from -7 to -5.5 kcal/mol [31,[54], [55], [56], [57]]. Wide range of molecular interactions was reported for the binding of alkaloids with lysozyme. Coralyne actively uses hydrophobic interaction for binding to lysozyme whereas sanguianrine interacts primarily through both hydrogen bonding and hydrophobic interaction [40,56].The binding of the iminium form of chelerythrine with lysozyme is a ground state endothermic process characterized by hydrophobic interactions whereas the binding of alkanolamine form of chelerythrine to lysozyme is an exothermic process primarily driven by hydrogen bonding [31]. Several alkaloids like coralyne, sanguinarine, quinolidine derivative etc. can markedly retard lysozyme fibrillation process with their unique binding capacity primarily through H-bonding and hydrophobic interactions [40,56,58].

Palmatine (Fig. 1) is naturally available protoberberine isoquinoline alkaloid that is generally used as folk medicine in China [59]. It is found in several plants including Chinese gold thread, Gurjo or heart-leaved moonseed, Amur cork tree etc. Many scientific reports suggested that palmatine has pharmacological effects like antioxidation, antiviral, antibacterial, antiinflammatory, neuroprotection, anticancer and regulator of blood lipid control [[60], [61], [62], [63], [64], [65], [66]]. In light of its myriad pharmacological effects we chose this medicinally important alkaloid palmatine as a potential candidate for combating the protein aggregation related ailments. Hen egg white lysozyme and human lysozyme display high scale homologous behaviour including their misfolding and unfolding property which leads to different disorders as mentioned earlier [67]. So in this work we have used hen egg white lysozyme to analyze the antiamyloidogenic behaviour of palmatine for the first time in the quest for designing therapeutics for protein aggregation related ailments.