Lichens as a potential natural source of bioactive compounds: a review

Biological activity of material whether known in folk medicine or observed in planned screening program has been the starting point in the drug research. The general pattern is the isolation of active principles, elucidation their structures, followed by attempts for modulation of its activity potential by chemical modification. Lichens are valuable plant resources and are used as medicine, food, fodder, perfume, spice, dyes and for miscellaneous purposes throughout the world. Lichens are well known for the diversity of secondary metabolites that they produce. Compounds isolated from various lichen species have been reported to display diverse biological activities. Here we review the medicinal efficacy of lichen substances, which intends to explore the pharmaceutical potential of lichen substances.     

Olive stone an attractive source of bioactive and valuable compounds

The olive stone and seed are an important byproduct generated in the olive oil extraction and pitted table olive industries. As a lignocellulosic material, the hemicellulose, cellulose and lignin are the main components of olive stone as wells as protein, fat, phenols, free sugars and poliols composition. The main use of this biomass is as combustion to produce electric energy or heat. Other uses such as activated carbon, furfural production, plastic filled, abrasive and cosmetic or other potential uses such as biosorbent, animal feed or resin formation have been cited. In this article, an overview of the characterization and main uses of olive stone and seed are described for the first time. Also, this review discusses the potential use of this material based on each component. In this way, a new approach to the olive stone and seed by pretreating with a steam explosion followed by chemical fractionation is described.     

Screening of the Antarctic marine sponges (Porifera) as a source of bioactive compounds

Sponges (Porifera) currently represent one of the richest sources of natural products and account for almost half of the pharmacologically active compounds of marine origin. However, to date very little is known about the pharmacological potential of the sponges from polar regions. In this work we report on screening of ethanolic extracts from 24 Antarctic marine sponges for different biological activities. The extracts were tested for cytotoxic effects against normal and transformed cell lines, red blood cells, and algae, for modulation of the activities of selected physiologically important enzymes (acetylcholinesterase, butyrylcholinesterase, and α-amylase), and for inhibition of growth of pathogenic and ecologically relevant bacteria and fungi. An extract from Tedania (Tedaniopsis) oxeata was selectively cytotoxic against the cancer cell lines and showed growth inhibition of all of the tested ecologically relevant and potentially pathogenic fungal isolates. The sponge extracts from Isodictya erinacea and Kirkpatrickia variolosa inhibited the activities of the cholinesterase enzymes, while the sponge extracts from Isodictya lankesteri and Inflatella belli reduced the activity of α-amylase. Several sponge extracts inhibited the growth of multiresistant pathogenic bacterial isolates of different origins, including extended-spectrum beta-lactamase and carbapenem-resistant strains, while sponge extracts from K. variolosa and Myxilla (Myxilla) mollis were active against a human methicillin-resistant Staphylococcus aureus strain. We conclude that Antarctic marine sponges represent a valuable source of biologically active compounds with pharmacological potential.     

Isolation of new actinomycete strains for the screening of new bioactive compounds

In order to facilitate the discovery of novel bioactive compounds from microorganisms, various techniques for isolation of new actinomycete strains have been attempted. Studies of the vertical distribution of actinomycetes in soil, isolation of actinomycetes from desert soils or fallen leaves, selective isolation of Kitasatospora strains using novobiocin or Actinoplanes strains using the chemotactic method, and the use of gellan gum as a solidifying agent were carried out. We discovered 9 novel bioactive compounds from actinomycete strains isolated under unusual conditions, and proposed two new genera, five new species and one new subspecies.     

The himanimides,new bioactive compounds from Serpula himantoides (Fr.) Karst

In a screening of basidiomycete cultures from Chile for the production of antibiotics we identified a Serpula himantoides strain as a producer of metabolites inhibiting the growth of bacteria and fungi. Bioactivity guided purification resulted in the isolation of four new antibiotics. Their structures were elucidated by spectroscopic methods. All four compounds are succinimide and maleimide derivatives, of which two are N-hydroxylated.     

Fungal endophytes from leaves of Avicennia marina growing in semi-arid environment as a promising source for bioactive compounds

Endophytic fungi are broadly dispersed residing inside plant tissues and have been demonstrated as a treasure for bioactive natural products. Unexplored harsh and heavy metal contaminant habitat of Avicennia marina may have diverse and potential fungal association. Therefore, this work aimed to isolate the culturable fungal endophytes associated with leaves of A. marina and to evaluate their medical potentialities. Seventeen isolates of endophyte fungi were isolated from healthy leaves and their antimicrobial activities were evaluated. Results showed that isolates had activity against micro-organisms in addition to their antioxidant activity produced a variety of phenolic compounds, besides exhibited a lowest cytotoxicity against ATCC-CCL-81 cell line. Consequently, selected endophytic fungal isolates were identified genetically as Chaetomium sp., Chaetomium madrasense, Chaetomium sp., Chaetomium globosum, Aspergillus hiratsukae, Aspergillus ochraceus, Alternaria tenuissima and Curvularia lunata with gene bank accession numbers MT089951, MT089952, MT089953, MT089954, MT089955, MT089956, MT089957 and MT089958 respectively. The most potent fungus extract was analysed using Gas chromatography–mass spectrometry which verified the presence of numerous bioactive compounds. These findings confirmed that new endophytic fungal strains derived from A. marina thrive in harsh ecosystem produce bioactive metabolites which can be recommended as a novel source for drug discovery.     

Penicillium verruculosum SG: a source of polyketide and bioactive compounds with varying cytotoxic activities against normal and cancer lines

A newly isolated fungus Penicillium verruculosum SG was evaluated for the production and characterization of bioactive colored secondary metabolites using solid-state fermentation along with their cytotoxic activities against normal and cancer cell lines. Logical fragmentation pattern following column chromatography, thin layer chromatography and liquid chromatography and mass spectrometry of crude culture filtrate of fungus revealed the presence of different polyketide pigments and other bioactive compounds. Cytotoxicity of the selected colored fractions of fungal filtrate containing different compounds revealed IC50 (μg/ml) values ranging from 5 to 100. It was significantly higher in case of orevactaene (5 + 0.44) and monascorubrine followed by pyripyropene (8 + 0.63) against cancer cell line KA3IT. Overall, these compounds considerably showed less toxicity toward normal cell lines NIH3T3, HSCT6, HEK293 and MDCK. XRD of a yellow crystalline compound (224.21 m/z) confirmed its 3-dimensional structure as phenazine 1 carboxylic acid (C13H8N2O2) (broad spectrum antibiotic), and it is first time reported in fungi.     

Bacterial diversity from benthic mats of Antarctic lakes as a source of new bioactive metabolites

During the MICROMAT project, the bacterial diversity of microbial mats growing in the benthic environment of Antarctic lakes was accessed for the discovery of novel antibiotics. In all, 723 Antarctic heterotrophic bacteria belonging to novel and/or endemic taxa in the α-, β- and γ-subclasses of the Proteobacteria, the Bacteroidetes branch, and of the high and low percentage G+C Gram-positives, were isolated, cultivated in different media and at different temperatures, and then screened for the production of antimicrobial activities. A total of 6348 extracts were prepared by solid phase extraction of the culture broths or by biomass solvent extraction. 122 bacteria showed antibacterial activity against the Gram-positives Staphylococcus aureus and to a lower extent Enterococcus faecium, and versus the Gram-negative Escherichia coli. Few of these strains showed also some antifungal activity against Cryptococcus neoformans, Aspergillus fumigatus and to a lower extent Candida albicans. LC–MS fractionation of extracts from a subset of strains (hits) that exhibited relatively potent antibacterial activities evidenced a chemical novelty that was further investigated. Two strains of Arthrobacter agilis produced potent antibacterial compounds with activity against Gram-positives and possibly related to novel cyclic thiazolyl peptides. To our knowledge, this is the first report of new antibiotics produced by bacteria from benthic microbial mats from Antarctic lakes. With no doubts these microbial assemblages represent an extremely rich source for the isolation of new strains producing novel bioactive metabolites with the potential to be developed as antibiotic compounds.     

Marine microorganisms as a source of bioactive agents

Several ecological factors of the marine environment were used in developing a strategy for discovering useful bioactive agents from marine microorganisms. By consideration of sea water requirements, production and degradation of marine polymers, and plasmid content, several novel anti-malarial antibiotics, anti-tumor polysaccharides, glucan-degrading enzymes, and aminoglycoside antibiotics were found.     

Sus Scrofa immune tissues as a new source of bioactive substances for skin wound healing

Influence of a new protein-peptide complex on promoting skin wound healing in male BALB/c mice was studied. Protein-peptide complex, extracted from Sus scrofa immune organs, was percutaneously administered using two methods: by lecithin gel-like liquid crystals and by liquid microemulsion. On the fifth day, wound closure in mice with a linear wound model become faster in group (less 2 days comparison to other ones), which was treated with lecithin liquid crystals carrying the protein-peptide complex. This promoting healing can be caused by resorption of bioactive high-molecular compounds the animal skin. In mice with the linear wound model, the tensile strength of the scars were respectively higher both in mice, treated using lecithin liquid crystals with protein-peptide complex, and in mice, treated using microemulsion containing protein-peptide complex, by 215.4% and 161.5% relative to the animals, which did not receive bioactive substances for wound treatment. It was associated with the regeneratory effects of tissue- and species-specific protein-peptide complexes, including α-thymosin Sus scrofa (C3VVV8_PIG, m/z 3802.8) and other factors, which were described as parts of the new extracted complex. This reveals that percutaneous administration of the complex reliably activates local regenerative processes in animals.     

In vitro culture of the endangered plant Eryngium viviparum as dual strategy for its ex situ conservation and source of bioactive compounds

Different Eryngium species have been used with ornamental, agricultural and medicinal purposes, as a consequence of their chemical constituents. In the southwest Europe the endemic Eryngium viviparum, presents a high risk of extinction and ex situ strategies are high recommended for efficient conservation and re-introduction program. The objective of this study was to satisfy a dual objective: (i) to develop an ex situ conservation strategy through micropropagation and (ii) taking advantage of the extraordinary potential of plant tissue culture, produce a considerable amount of plant material to carry out a preliminary phytochemical study, based on the accumulation of phenolic compounds and their associated antioxidant activity. First a factorial design was conducted in order to study the effect of two cytokinins (6- benzylaminopurine, BAP, and kinetin, KIN), at three levels (0, 1 and 2 mg L^?1), on shoot multiplication. Later another factorial design was applied, by using three levels of MS medium salt strength (full, half and quarter- strength) and four sucrose levels (0, 1, 2, and 3%) for improving shoot elongation and rooting. In parallel, a preliminary quantification of total phenolic and flavonoid contents from E. viviparum aerial parts was determined. The simple micropropagation protocol designed allowed obtaining a high rates of shoot multiplication (5.1–5.8 new shoots), rooting (100%) with healthy long roots (3.1–3.5 cm) and plantlet acclimatization (96%). Moderate antioxidant activity was recorded in hydromethanolic extracts from E. viviparum aerial parts. High correlation between total phenolic content and BAP levels in the culture media was found. In conclusion, the micropropagation procedure described here for the endangered E. viviparum can be used as new and very efficient ex situ conservation strategy, and as potential source of antioxidants, conferring an added-value to this plant.

     

Deciphering chemical profiling,pharmacological responses and potential bioactive constituents of Saussurea lappa Decne. Extracts through in vitro approaches

Despite advancement in modern medicines, plant derived medicines have still wide range utilities as they have less side effects and are cheap and biocompitable. Sassurea lappa is an extensively used plant in traditional medicinal formulations. Plant roots are used to cure various diseases including cancer, rheumatic pain, abdominal and nervous disorders. The present study was aimed for the evalution of biological potentials of methanolic and chloroform extracts of Saussurea lappa root, leaf, seed and flower. The methanolic and chloroform extracts were subjected to qualitative and quantitative phytochemical analyses. Identification of functional groups was performed using Fourier Transform infrared (FT-IR) spectroscopy. Antioxidant potential was determined via diphenyl-1-picrylhydrazyl (DPPH), total reducing power (TRP) and total antioxidant capacity (TAC) method, anti-hemolytic potential was conducted on human RBCs, antibacterial activity was evaluated against six American type culture collection (ATCC) and three multi drug resistance (MDR) strains, cytotoxic and phytotoxic potentials were evaluated through brine shrimp lethality assay and raddish seed assay respectively. Experiments were performed in triplicates and analysis of variance (ANOVA) was applied using statistics version-8.1. Phytochemical analysis revealed the presence of sixteen secondary metabolites. Fourteen functional groups were identified through FTIR. S. lappa root methanolic (SLRM) showed maximum antioxidant activity index (AAI-79.42%) whereas chloroform extract of leaves (SLLC) gave highest antibacterial activity with maximum zone of inhibition (ZOI) against Pseudomonas aeruginosa (21.4 mm). Maximum cytotoxicity was observed for SLRM with lethal dose concentration (LC₅₀) of 58.8 µg/mL. However, root extracts showed significant phytotoxicity (15% germination). The current study investigated that bioactive compounds present in S. lappa leaves, seed, flower and roots were responsible for enhanced biological potentials. Further studies on isolation and characterization of these bioactive compounds may help in drug development. In future, we recommend different in-vitro and in-vivo studies to further confirm it biopharmacological potencies.     

High-throughput screening of bioactive compounds via new catalytic reaction in the pooled mixture

To increase the chances of finding new candidate molecules with medicinal properties, while expending less resource and effort, the present study used pooled substrates as starting materials. A bisindole compound that showed inhibitory activity was then isolated from the mixture, and the activity was improved by optimizing the substituents on the indole skeleton.     

Activity-guided screening of bioactive natural compounds implementing a new glucocorticoid-receptor-translocation assay and detection of new anti-inflammatory steroids from bacteria

Using an in vitro cell-based assay in a flow-design, we have applied activity-guided screening to search for new bioactive compounds isolated from microorganisms. A first assay employs the stable expression of nuclear factor kappa B (NF-κB) while a second assay utilizes the glucocorticoid receptor (GR) coupled to green fluorescent protein. A specialized assay was implemented for both the translocation of NF-κB and to inhibit the translocation of cytokine-mediated NF-κB. In addition, we developed in a wide palette of cell lines used for a highly specialized GR-translocation assay to detect anti-inflammatory effects. This approach demonstrates the straight-forward combination of cell-based assays arranged with an automated fluorescence microscope. This allows for the direct sorting of extracts which are acting in a pharmaceutically interesting way. Initial results using this technique have led to the detection of new anti-inflammatory steroids from bacterial crude extracts.     

Agricultural residues as a source of bioactive natural products

Agricultural industry produces billions of tons of residues in non-edible portions derived from the cultivation and processing of a particular crop. These residues can cause pollution, management and economic problems worldwide. This is the reason for the development of different strategies to use agricultural and industrial residues as a source of high value-added products. This review gives an overview of the potential of agricultural residues as raw materials for the production of bioactive products considering their availability, processing, and their chemical and biological properties. We also provide new data on the potential as biopesticides of some selected crop- and processing-based residues.