In vitro and in silico cholinesterase inhibitory potential of metabolites from Laurencia snackeyi (Weber-van Bosse) M. Masuda

Alzheimer's disease (AD) is a neurodegenerative disease that causes deterioration in intelligence and psychological activities. Yet, till today, no cure is available for AD. The marine environment is an important sink of bioactive compounds with neuroprotective potential with reduced adverse effects. Recently, we collected the red algae Laurencia snackeyi from Terumbu Island, Malaysia which is known to be rich in halogenated metabolites making it the most sought-after red algae for pharmaceutical studies. The red alga was identified based on basic morphological characteristics, microscopic observation and chemical data from literature. The purplish-brown algae was confirmed a new record. In Malaysia, this species is poorly documented in Peninsular Malaysia as compared to its eastern continent Borneo. Thus, this study intended to investigate the diversity of secondary metabolites present in the alga and its cholinesterase inhibiting potential for AD. The extract inhibited both acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with IC50 values of  14.45 ± 0.34 μ g mL-1 and 39.59 ± 0.24 μ g mL-1, respectively. Subsequently, we isolated the synderanes, palisadin A (1), aplysistatin (2) and 5-acetoxypalisadin B (3) that was not exhibit potential. Mass spectrometry analysis detected at total of 33 additional metabolites. The computational aided molecular docking using the AChE and BChE receptors on all metabolites shortlisted 5,8,11,14-eicosatetraynoic acid (31) and 15-hydroxy-1-[2-(hydroxymethyl)-1-piperidinyl]prost-13-ene-1,9-dione (42) with best inhibitory properties, respectively with the lowest optimal combination of S-score and RMSD values. This study shows the unexplored potential of marine natural resources, however, obtaining sufficient biomass for detailed investigation is an uphill task. Regardless, there is a lot of potential for future prospects with a wide range of marine natural resources to study and the incorporation of synthetic chemistry, in vivo studies in experimental design.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03725-6.

Antimicrobial Potential of Aqueous Extract of Giant Sword Fern and Ultra-High-Performance Liquid Chromatography-High-Resolution Mass Spectrometry Analysis

Vibriosis and parasitic leech infestations cause the death of various farmed fish, such as groupers, hybrid groupers, sea bass, etc., in Malaysia and other Southeast Asian countries. In the absence of natural control agents, aquaculture operators rely on toxic chemicals to control Vibrio infections and parasitic leeches, which can have a negative impact on the environment and health. In the present study, we investigated the antivibrio and antiparasitic activities of the aqueous extract of giant sword fern (GSF) (Nephrolepis biserrata, Nephrolepidaceae, locally known as "Paku Pedang") against four Vibrio spp. and the parasitic leech Zeylanicobdella arugamensis, as well as its metabolic composition using the ultra-high-performance liquid chromatography-high-resolution mass spectrometry system (UHPLC-HRMS). The data show that the aqueous extract of GSF at a concentration of 100 mg/mL exhibits potent bactericidal activity against V. parahaemolyticus with a zone of inhibition of 19.5 mm. In addition, the extract showed dose-dependent activity against leeches, resulting in the complete killing of the parasitic leeches within a short period of 11-43 min when tested at concentrations ranging from 100 to 25 mg/mL. The UHPLC-HRMS analysis detected 118 metabolites in the aqueous extract of GSF. Flavonoids were the primary metabolites, followed by phenolic, aromatic, fatty acyl, terpenoid, vitamin and steroidal compounds. Notably, several of these metabolites possess antibacterial and antiparasitic properties, including cinnamaldehyde, cinnamic acid, apigenin, quercetin, cynaroside, luteolin, naringenin, wogonin, 6-gingerol, nicotinamide, abscisic acid, daidzein, salvianolic acid B, etc. Overall, our study shows the significant antibacterial and antiparasitic potential of the GSF aqueous extract, which demonstrates the presence of valuable secondary metabolites. Consequently, the aqueous extract is a promising natural alternative for the effective control of Vibrio infections and the treatment of parasitic leeches in aquaculture systems.

Hypoglycaemic Molecules for the Management of Diabetes Mellitus from Marine Sources

Diabetes mellitus (DM) is a chronic metabolic disorder recognized as a major health problem globally. A defective insulin activity contributes to the prevalence and expansion of DM. Treatment of DM is often hampered by limited options of conventional therapies and adverse effects associated with existing procedures. This has led to a spike in the exploration for potential therapeutic agents from various natural resources for clinical applications. The marine environment is a huge store of unexplored diversity of chemicals produced by a multitude of organisms. To date, marine microorganisms, microalgae, macroalgae, corals, sponges, and fishes have been evaluated for their anti-diabetic properties. The structural diversity of bioactive metabolites discovered has shown promising hypoglycaemic potential through in vitro and in vivo screenings via various mechanisms of action, such as PTP1B, α-glucosidase, α-amylase, β-glucosidase, and aldose reductase inhibition as well as PPAR alpha/gamma dual agonists activities. On the other hand, hypoglycaemic effect is also shown to be exerted through the balance of antioxidants and free radicals. This review highlights marine-derived chemicals with hypoglycaemic effects and their respective mechanisms of action in the management of DM in humans.

Vaccine for Diabetes-Where Do We Stand?

Diabetes is an endocrinological disorder with a rapidly increasing number of patients globally. Over the last few years, the alarming status of diabetes has become a pivotal factor pertaining to morbidity and mortality among the youth as well as middle-aged people. Current developments in our understanding related to autoimmune responses leading to diabetes have developed a cause for concern in the prospective usage of immunomodulatory agents to prevent diabetes. The mechanism of action of vaccines varies greatly, such as removing autoreactive T cells and inhibiting the interactions between immune cells. Currently, most developed diabetes vaccines have been tested in animal models, while only a few human trials have been completed with positive outcomes. In this review, we investigate the undergoing clinical trial studies for the development of a prototype diabetes vaccine.

First record of the fungal genus Neodevriesia Quaedvl. & Crous (Ascomycota, Dothideomycetes, Neodevriesiaceae) isolated from scleractinian corals of Perhentian Islands, Malaysia

Fungal species members of the genus Neodevriesia have been known to occur in marine environments. This report documents the first record of the fungal genus Neodevriesia isolated from scleractinian corals. Three isolated strains were identified from a phylogenetic tree that was constructed, based on the nuclear ribosomal internal transcribed spacer and partial large subunit (ITS + LSU) DNA sequences. Isolates were closely related to both Neodevriesiashakazului (Crous) Crous and Neodevriesiaqueenslandica (Crous, R.G. Shivas & McTaggart) Crous, but formed a distinct clade with strong support that implies a potentially genetic variant of a known species or even a novel species. These findings contribute to the fungal diversity checklist in Malaysia and knowledge about marine fungi associated with scleractinian corals.

Nutritional Profile, Antioxidative and Antihyperglycemic Properties of Padina tetrastromatica from Tioman Island, Malaysia

Seaweeds are an important ingredient of functional foods recommended for daily food, due to their unique compositions and nutritional value. Padina tetrastromatica is a brown edible seaweed that is commonly found along the coastal regions of Peninsular Malaysia and consumed as food by some coastal communities. This study investigates the nutritional and antihyperglycaemic potential of P. tetrastromatica extracts, which is generally accepted as an important functional food. In our methodology, we induced diabetes intraperitoneally in experimental animals with a dose of 65 mg kg-1 body weight of streptozotocin. Oral treatment with 200 and 400 mg kg-1 of P. tetrastromatica ethanolic and ethyl acetate extracts were initiated, respectively, to experimental rats once daily for 18 days. Metformin was used as the positive control. Biochemical estimations and histopathological analysis were included in this study. Treatment with P. tetrastromatica extracts significantly lowered the plasma glucose levels in Streptozotocin-induced diabetic rats. In addition, P. tetrastromatica extract treatment also showed a significant reduction in serum alanine transaminase levels. However, no significant changes were observed in serum aspartate transaminase levels. The ethyl acetate extract of P. tetrastromatica at 400 mg kg-1 dose shows some nephroprotective effect, which is observed from the significant increase in the plasma albumin levels. Histopathological evaluation revealed no marked morphological changes in tissues of the isolated organs of the ethyl acetate extract-treated group, revealing the safe nature of P. tetrastromatica.

Middle East Respiratory Syndrome (MERS) Virus-Pathophysiological Axis and the Current Treatment Strategies

Middle East respiratory syndrome (MERS) is a lethal respiratory disease with its first case reported back in 2012 (Jeddah, Saudi Arabia). It is a novel, single-stranded, positive-sense RNA beta coronavirus (MERS-CoV) that was isolated from a patient who died from a severe respiratory illness. Later, it was found that this patient was infected with MERS. MERS is endemic to countries in the Middle East regions, such as Saudi Arabia, Jordan, Qatar, Oman, Kuwait and the United Arab Emirates. It has been reported that the MERS virus originated from bats and dromedary camels, the natural hosts of MERS-CoV. The transmission of the virus to humans has been thought to be either direct or indirect. Few camel-to-human transmissions were reported earlier. However, the mode of transmission of how the virus affects humans remains unanswered. Moreover, outbreaks in either family-based or hospital-based settings were observed with high mortality rates, especially in individuals who did not receive proper management or those with underlying comorbidities, such as diabetes and renal failure. Since then, there have been numerous reports hypothesising complications in fatal cases of MERS. Over the years, various diagnostic methods, treatment strategies and preventive measures have been strategised in containing the MERS infection. Evidence from multiple sources implicated that no treatment options and vaccines have been developed in specific, for the direct management of MERS-CoV infection. Nevertheless, there are supportive measures outlined in response to symptom-related management. Health authorities should stress more on infection and prevention control measures, to ensure that MERS remains as a low-level threat to public health.

Bioprospecting Cultivated Tropical Green Algae, Caulerpa racemosa (Forsskal) J. Agardh: A Perspective on Nutritional Properties, Antioxidative Capacity and Anti-Diabetic Potential

Caulerpa racemosa (Forsskal) J. Agardh is a green seaweed used as food and folk medicine since ancient times in the Indo-Pacific region, particularly in southeast Asia. In this study, the proximate nutrient composition, phytochemical, anti-oxidant and anti-diabetic properties of sea grape C. racemosa collected from culture fishponds in Johor, Malaysia were analysed. The contents (dry weight basis) of carbohydrate, crude protein, crude lipids, ash and caloric value obtained were 33.42 ± 1.34%, 20.27 ± 0.14%, 4.20 ± 0.32%, 28.25 ± 0.27% and 2544.67 ± 7.04 cal g-1, respectively. The amino acid score (AAs) and biological protein value (213.43 mg g-1) indicated that C. racemosa presented a better protein quality. The most abundant fatty acids were C16:0 (palmitic acid: 63.27%), followed by C18:1 (oleic acid: 5.80%), and C18:2 ῳ6 (linoleic acid: 5.33%). The analysis of the ash content indicated that essential minerals and trace elements, such as Ca, Fe, and Mn, were present in the seaweed. The total phenolic content (TPC) and total flavonoid content (TFC) observed in the ethyl acetate extract were 17.88 ± 0.78 mg GAE g-1 and 59.43 ± 2.45 mg QE g-1, respectively. The ethyl acetate extract of C. racemosa demonstrated notable anti-diabetic activity in diabetic induced rats. The low (100 mg kg-1) and high (200 mg kg-1) doses of cultivated C. racemosa extract exhibited a significant decrease (p < 0.05) in blood glucose levels while preventing weight loss, reducing plasma AST, ALT levels as a sign of hepatoprotective effect and recording albumin levels similar to positive control in diabetic induced rats. The results support the usefulness of cultivated C. racemosa as a potential functional food.

Effects of Seasonal Variability on the Physicochemical, Biochemical, and Nutritional Composition of Western Peninsular Malaysia Gracilaria manilaensis

This study evaluated the effect of seasonal variation on the physicochemical, biochemical, and nutritional composition of Gracilaria manilaensis. Sampling was designed during the main monsoon seasons in Malaysia-the Southwest monsoon (SWM) and Northeast monsoon (NEM)-to understand the intraspecific variation (p < 0.05). Carbohydrates, protein, and dietary fiber were found to be higher in NEM-G. manilaensis, whereas a higher ash content was quantified in SWM-G. manilaensis. No significant differences were found in crude lipid and moisture content (p > 0.05). Vitamin B2 was calculated as (0.29 ± 0.06 mg 100 g^-1) and (0.38 ± 0.06 mg 100 g^-1) for the NEM and SWM samples, respectively (p < 0.05). The fatty acid profile showed the dominance of saturated fatty acids (SFAs)-palmitic acids, stearic acid, and myristic acid-while the mineral contents were found to be good sources of calcium (1750.97-4047.74 mg 100 g^-1) and iron (1512.55-1346.05 mg 100 g^-1). Tryptophan and lysine were recorded as the limiting essential amino acids (EAAs) in NEM G. manilaensis, while leucine and phenylalanine were found to be the limiting EAAs in the SWM samples. None of the extracts exhibited antibacterial properties against the screened strains. The study concluded that seasonal changes have a great effect on the biochemical composition of G. manilaensis.

Impact of Land-use Change on Vertical Soil Bacterial Communities in Sabah

Decline in forest productivity due to forest conversion is defining the Bornean landscape. Responses of bacterial communities due to land-use changes are vital and could define our understanding of ecosystem functions. This study reports the changes in bacterial community structure in organic soil (0-5 cm; O-Horizon) and organic-mineral soil (5-15 cm; A-Horizon) across Maliau Basin Conservation Area old growth forest (MBOG), Fragment E logged forest (FELF) located in Kalabakan Forest Reserve to Benta Wawasan oil palm plantation (BWOP) using two-step PCR amplicon analysis of bacteria DNA on Illumina Miseq next generation sequencing. A total of 30 soil samples yielded 893,752-OTU reads at ≥97% similarity from 5,446,512 good quality sequences. Soil from BWOP plantation showed highest unshared OTUs for organic (49.2%) and organic-mineral (50.9%) soil. MBOG soil showed a drop in unshared OTUs between organic (48.6%) and organic-mineral (33.9%). At phylum level, Proteobacteria dominated MBOG but shifted to Actinobacteria in logged and plantation soil. Present findings also indicated that only FELF exhibited change in bacterial communities along the soil depth, moving from the organic to the organic-mineral layer. Both layers of BWOP plantation soils deviated from other forests' soil in β-diversity analysis. To our knowledge, this is the first report on transitions of bacterial community structures with different soil horizons in the tropical rainforest including Borneo, Sabah. Borneo tropical soils form a large reservoir for soil bacteria and future exploration is needed for fully understanding the diversity structure and their bacterial functional properties.

Manoalide-related Sesterterpene from the Marine SpongeLuffariella variabilis

A new manoalide-related sesterterpene, (4 E,6 E)-dehydro-25- O-methylmanoalide (1), was isolated from the organic extracts of the Bornean marine sponge Luffariella variabilis, together with the known compound (4 E,6 E)-dehydromanoalide (2). The structure of compound 1 was elucidated by interpretation of its spectroscopic data.

Capgermacrenes A and B, Bioactive Secondary Metabolites from a Bornean Soft Coral, Capnella sp

Two new bicyclogermacrenes, capgermacrenes A (1) and B (2), were isolated with two known compounds, palustrol (3) and litseagermacrane (4), from a population of Bornean soft coral Capnella sp. The structures of these metabolites were elucidated based on spectroscopic data. Compound 1 was found to inhibit the accumulation of the LPS-induced pro-inflammatory IL-1β and NO production by down-regulating the expression of iNOS protein in RAW 264.7 macrophages.

2-Acetoxyverecynarmin C, a new briarane COX inhibitory diterpenoid from Pennatula aculeata

A new briarane-type diterpenoid, named 2-acetoxyverecynarmin C, was isolated from the methanolic extract of an octocoral, Pennatula aculeata, that exhibited cyclooxygenase (COX) inhibitory activity. The structure of the compound was elucidated by ESI-HRMS, 1D and 2D NMR spectroscopy and comparison of the measured spectral data with those reported in the literature. The relative stereochemistry at chiral carbons was established from 2D NOESY experiments. 2-Acetoxyverecynarmin C is a tricyclic compound containing a furan ring at C-7,8 of a briarane skeleton. 2-Acetoxyverecynarmin C showed moderate inhibitory activity in in vitro COX-1 and COX-2 assays.

2-Acetoxyverecynarmin C, a New Briarane COX Inhibitory Diterpenoid from Pennatula aculeata

A new briarane-type diterpenoid, named 2-acetoxyverecynarmin C, was isolated from the methanolic extract of an octocoral, Pennatula aculeata, that exhibited cyclooxygenase (COX) inhibitory activity. The structure of the compound was elucidated by ESI-HRMS, 1D and 2D NMR spectroscopy and comparison of the measured spectral data with those reported in the literature. The relative stereochemistry at chiral carbons was established from 2D NOESY experiments. 2-Acetoxyverecynarmin C is a tricyclic compound containing a furan ring at C-7,8 of a briarane skeleton. 2-Acetoxyverecynarmin C showed moderate inhibitory activity in in vitro COX-1 and COX-2 assays.

Essential oil composition, cytotoxic and antibacterial activities of five Etlingera species from Borneo

Essential oils obtained by hydrodistillation from the rhizomes of Etlingera pyramidosphaera (K. Schum.) R. M. Sm, E. megalocheilos (Griff.) A.D. Poulsen, comb. nov., E. coccinea (Blume) S. Sakai & Nagam, E. elatior (Jack) R. M. Sm, and E. brevilabrum (Valeton) R. M. Sm were analyzed by GCMS. The highest oil yield was obtained from E. pyramidosphaera (0.45%), followed by E. elatior (0.38%), E. coccinea (0.30%), E. brevilabrum (0.28%) and E. megalocheilos (0.25%). The major constituents of the essential oils were oxygenated monoterpenes, followed by sesquiterpenes, oxygenated sesquiterpenes, oxygenated diterpenes and diterpenes. The essential oils from E. pyramidosphaera and E. brevilabrum exhibited the best cytotoxicity against MCF 7 (LC50: 7.5 +/- 0.5 mg mL(-1)) and HL 60 (LC50: 5.0 mg mL(-1)), respectively. Strong inhibition was also observed for the essential oils of E. coccinea and E. megalocheilos against Staphylococcus aureus (MIC: 8.0 +/- 0.5 mg mL(-1), and 5.0 +/- 0.5 mg mL(-1)) and Streptococcus pyrogenes (MIC: 6.0 +/- 0.5 mg mL(-1) and 8.0 +/- 0.5 mg mL(-1)).