Characterization of peptide-rich secretions from sex-differentiated odontophrynus americanus with cholinesterase inhibitory, antioxidant, and metal chelating activities

Title : Characterization of peptide-rich secretions from sex-differentiated odontophrynus americanus with cholinesterase inhibitory, antioxidant, and metal chelating activities

Abstract:

Amphibians secrete a wide variety of bioactive molecules, with peptides being the most abundant and functionally diverse. Despite their established therapeutic potential, sex-based differences in amphibian skin secretions remain largely unexplored. In this study, we characterize the peptide-rich skin secretions of Odontophrynus americanus, a native anuran species from the Argentine Litoral; evaluating biochemical, functional, and toxicity differences between males (Oa-M) and females (Oa-F), with particular relevance to Alzheimer's disease (AD). Given the multifactorial nature of AD—characterized by cholinergic dysfunction, oxidative stress, and metal dyshomeostasis—natural compounds with multi-target activity, such as amphibian peptides, represent a promising therapeutic strategy.

Analytical characterization including bicinchoninic acid assays, thin-layer chromatography (TLC), and high-performance liquid chromatography (HPLC) confirmed the near-exclusive presence of peptides in both male and female skin secretions, with minor sex-related variations.

Both secretions demonstrated inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) (~40%), key targets in AD therapy. Cholinesterase inhibition is crucial in the search for anti-AD drugs, as it may help increase acetylcholine levels to enhance cognitive function, while also potentially addressing neuroinflammation and amyloid aggregation. Moreover, both secretions exhibited potent antioxidant activity (EC₅₀: 48–49 μg/mL) and Fe²⁺-chelating properties (EC₅₀: 107–156 μg/mL), reinforcing their neuroprotective potential. Notably, both Oa-M and Oa-F secretions prevented lipid peroxidation by 90–100% over five days, emphasizing their role in mitigating oxidative stress, a major contributor to neurodegeneration. Toxicity assays revealed that both secretions were well-tolerated, with low hemolytic activity against human erythrocytes and low cytotoxicity in Artemia salina; although Oa-M was significantly less toxic. Overall, Oa-M and Oa-F exhibited comparable bioactivity profiles, with Oa-M showing slightly higher efficacy and much lower toxicity.

This study is the first to report sex-based biochemical and bioactivity differences in the skin secretions of O. americanus, providing valuable insights into amphibian molecular chemistry and broadening their potential biomedical applications. Future research will focus on the isolation and structural characterization of peptides, along with in vivo validation, aiming to develop novel therapeutic candidates for neurodegenerative diseases.

Biography:

Álvaro Rietmann has a BSc. in Biotechnology and is currently working at the Laboratorio de Péptidos Bioactivos, Department of Organic Chemistry, Faculty of Biochemistry and Biological Sciences FBCB, Universidad Nacional del Litoral. He is pursuing a PhD in Biological Sciences, focusing on the study of local amphibians as sources of multi-target molecules for treating neurodegenerative diseases such as Alzheimer’s and Parkinson’s. He has participated in 5 research articles in the last 3 years. He is also a Teaching Assistant at the Department of Organic Chemistry, FBCB-UNL.