siphonostelic ferns in which the medullary rays are narrow or lacking. These feature forms are interpreted as an evolutionary series in which the outstanding is the development of a stelar pith by means of a reduction of the central tracheids and their replacement finally by parenchyma. It would be difficult to prove or disprove this view. That a stelar pith might originate in this way or by an expansion of the stele, as in the roots of many of the higher plants, is unquestioned. But that these fossils represented evolutionary stages which culminated in the conversion of a part of a stelar pith into phloem and endodermis, as in Osmundites skidegatensis or Osmunda cinnamomea, is unsupported by evidence of any kind. GWYNNE-VAUGHAN and BOWER accept JEFFREY'S hypothesis as to the extrastelar character of the pith in every other family of ferns, but in dealing with the Osmundaceae they cloud the issue by apparently confusing two problems. From a limited series of imperfect fossils they have tried to discover when and how cortical tissues might have been enclosed by the stele. Failing in this, they conclude that they probably could not have been included at all. But neither are we sure when and how that happened in the other families, and a search through the known fossil representatives would probably end as unsatisfactorily as in the case of the Osmundacea~e. Research so far has been successful mainly in verifying the theory that the filicinean pith is extrastelar, and with such forms as Onoclea, in which the pith consists partly of epidermal tissues and the atmosphere, there is scarcely any escape from accepting it, just as these botanists have done. It is true that the evidence in Osmunda is not as striking as in Onoclea, but it is quite as striking as in many other forms with extrastelar piths. There are representatives of the Osmundaceae in which the central pith, peripheral pith, internal endodermis, and internal phloem are texturally like those of the outer cortex, inner cortex, external endodermis, and external phloem, and these respectively are continuous at times through leaf or branch gaps. Moreover, there are abundant instances of what in other groups would readily be conceded vestiges of portions of amphiphloic siphonosteles. Applying the same standards of interpretation of anatomical phenomena to all the Filicales, it seems reasonable to maintain that the kind of evidence that has carried conviction in every case but one must hold in all. The question as to when and how the extrastelar pith originated is quite another matter, and I venture to affirm that observations on such features as the relative position of a tracheid and a parenchyma cell in the xylem of a sporeling, or the shape of medullary rays in an adult, will help little in its solution.-J. H. FAULL.

Biology of Lichens

Antioxidant compounds from microbial sources: A review

Natural extracts are the source of many antioxidant substances. They have proven useful not only as supplements preventing diseases caused by oxidative stress and food additives preventing oxidation but also as system components for the production of metallic nanoparticles by the so-called green synthesis. This is important given the drastically increased demand for nanomaterials in biomedical fields. The source of ecological technology for producing nanoparticles can be plants or microorganisms (yeast, algae, cyanobacteria, fungi, and bacteria). This review presents recently published research on the green synthesis of nanoparticles. The conditions of biosynthesis and possible mechanisms of nanoparticle formation with the participation of bacteria are presented. The potential of natural extracts for biogenic synthesis depends on the content of reducing substances. The assessment of the antioxidant activity of extracts as multicomponent mixtures is still a challenge for analytical chemistry. There is still no universal test for measuring total antioxidant capacity (TAC). There are many in vitro chemical tests that quantify the antioxidant scavenging activity of free radicals and their ability to chelate metals and that reduce free radical damage. This paper presents the classification of antioxidants and non-enzymatic methods of testing antioxidant capacity in vitro, with particular emphasis on methods based on nanoparticles. Examples of recent studies on the antioxidant activity of natural extracts obtained from different species such as plants, fungi, bacteria, algae, lichens, actinomycetes were collected, giving evaluation methods, reference antioxidants, and details on the preparation of extracts.

https://www.mdpi.com/1996-1944/14/15/4135/pdf

Antioxidants: Classification, Natural Sources, Activity/Capacity Measurements, and Usefulness for the Synthesis of Nanoparticles.

The advancement in the knowledge of potent antioxidants has uncovered the way for greater insight in the treatment of diabetic complications. Lichens are a rich resource of novel bioactive compounds and their antioxidant potential is well documented. Herein we review the antidiabetic potential of lichens which have received considerable attention, in the recent past. We have correlated the antidiabetic and the antioxidant potential of lichen compounds. The study shows a good accordance between antioxidant and antidiabetic activity of lichens and points out the need to look into gathering the scarce and scattered data on biological activities for effective utilization. The review establishes that the lichen extracts, especially of Parmotrema sp. and Ramalina sp. have shown promising potential in both antidiabetic and antioxidant assays. Ubiquitous compounds, namely, zeorin, methylorsellinate, methyl-β-orcinol carboxylate, methyl haematommate, lecanoric acid, salazinic acid, sekikaic acid, usnic acid, gyrophoric acid, and lobaric acid have shown promising potential in both antidiabetic as well as antioxidant assays highlighting their potential for effective treatment of diabetic mellitus and its associated complications. The available compilation of this data provides the future perspectives and highlight the need for further studies of this potent herbal source to harvest more beneficial therapeutic antidiabetic drugs.

/pdf/potential-of-lichen-compounds-as-antidiabetic-agents-with-4zg18er361.pdf

Potential of Lichen Compounds as Antidiabetic Agents with Antioxidative Properties: A Review.

Several lichen species are reported to be used tradiationally in many theraupatic practices Many lichen species are reported as sources of several bioactive natural compounds Several lichen species of Nepal are so far chemically unexplored The morphological, anatomical and phytochemical characteristics of lichens were compared for the taxonomic identification of the species Methanol- water extract of lichens were sub fractionated into hexane, dichloromethane and methanol fractions for bioactivity assays Antimicrobial activities of extracts were evaluated agaisnt pathogenic bacteria and fungal species DPPH test was used for antioxidant potential evaluation Brineshrimp test was perfermed to evaluate toxicity of the extracts A total of 84 lichen specimens were collected and identified from Annapurna Conservation Area (ACA) Nepal The specimens were identified as belonging to 19 genera and 47 species Methanol fractions of 16 specimens and dichloromethane (DCM) fractions of 21 lichens specimens showed antioxidant activities comparable with commercial standards (BHA, Butylated hydroxyanisole, IC50=49±09 μg/mL) even at crude extract level Similarly, the DCM fraction of 17 lichens showed potential antimicrobial activity against a Gram-positive bacterium (Staphylococcus aureus KCTC3881) and DCM fractions of 45 lichens showed antimicrobial activity against a Gram-negative bacterium (Klebsiella pneumoniae KCTC2242) DCM fractions of three lichens showed antifungal activity against the yeast, Candida albicans KCTC 7965 Likewise, methanol fractions of 39 lichens and DCM fractions of 74 lichens showed strong toxicity against brine shrimp nauplii with more than 80% mortality Such biological activity-rich lichen specimens warrant further research on exploration of natural products with antioxidant, antimicrobial and anti cancer (toxic) potential

/pdf/investigation-of-antioxidant-antimicrobial-and-toxicity-425k4kgz6j.pdf

Investigation of antioxidant, antimicrobial and toxicity activities of lichens from high altitude regions of Nepal.

The present study was carried out to evaluate the antibacterial and antioxidant potential of acetone and methanol extracts of lichen (Parmotrema praesorediosum, P. rampoddense, P. tinctorum and P. reticulatum) and isolated chemical constituents which are praesorediosic acid, protocetraric acid, usnic acid, α–collatolic acid, β-alectoronic acid, atranorin and chloroatranorin. The antibacterial activity was evaluated using broth dilution method. Acetone extracts (except for P. reticulatum) showed good inhibitory activity against S. aureus and B. subtilis with MIC values ranging from 500–125 µg/mL, whereas, no activity was observed for the methanol extracts. Extracts exhibited zero inhibitory activity against E. coli. The antioxidant ability was measured using a DPPH free radical scavenging activity assay. Only methanol extract of P. praesorediosum exhibited more than 50% scavenging activity. Among the isolates, usnic acid exhibited the strongest antibacterial activity against S. aureus and B. subtilis with MIC value 7.81 µg/mL. Praesorediosic acid and protocetraric acid isolates exclusively inhibited E. coli at concentration 125 µg/mL and displayed results exceeding 50% scavenging activity (57.57% and 63.97%, respectively). Hitherto, it is the first evaluation of antibacterial activity on lichens of Malaysian origin and to our knowledge; the first reported study on the biological activity of praesorediosic acid and Parmotrema rampoddense.

Biological activities of four Parmotrema species of Malaysian origin and their chemical constituents

/pdf/antibacterial-and-antioxidant-activity-of-lichens-usnea-2qbs833mcb.pdf

Antibacterial and Antioxidant Activity of Lichens Usnea rubrotincta, Ramalina dumeticola, Cladonia verticillata and Their Chemical Constituents

The present study was carried out to evaluate the antibacterial activity of extract and chemical constituents of Usnea rubrotincta, Ramalina dumeticola and Cladonia verticillata. Extracts of U. rubrotincta and R. dumeticola showed promising antibacterial activity against gram positive bacteria Staphylococcus aureus and Bacillus subtilis. The lowest value of MIC (15.63 μg/mL) was observed for the acetone extract of U. rubrotincta against B. subtilis. While extract of C. verticillata was neither active against gram positive nor gram negative bacteria at the highest tested concentration of 500 μg/m. This is the first evaluation of antibacterial activity of lichens found in Malaysia and to our knowledge, this is the first report of antibacterial

Antibacterial activity of lichen Usnea rubrotincta, Ramalina dumeticola, and Cladonia verticillata

The present study was carried out to evaluate the antibacterial and antioxidant activity of extract and chemical constituents of Usnea rubrotincta, Ramalina dumeticola and Cladonia verticillata. Acetone extract of U. rubrotincta showed promising antibacterial activity against Gram positive bacteria Bacillus subtilis with the lowest Minimal Inhibitory Concentration (MIC) value of (15.63 µg/mL). Six secondary metabolites were isolated using Preparative High Performance Liquid Chromatography (PHPLC) method from the two bioactive lichens U. rubrotincta and R. dumeticola (compound 1 - 6). Among all six compounds, compound (1) exhibited strongest activity against both the tested Gram positive bacteria at 7.81 µg/mL. Compound (6) had 69.57% scavenging activity against DPPH free radical while the rest only showed below 50% scavenging activity. This is the first evaluation of antibacterial activity of lichens found in Malaysia and to our knowledge, this is the first report of antibacterial and antioxidant activity of compound (3) and (5).

/pdf/antibacterial-and-antioxidant-activity-of-lichens-usnea-2wlhz0l6r9.pdf

ANTIBACTERIAL AND ANTIOXIDANT ACTIVITY OF LICHENS Usnea rubrotincta, Ramalina dumeticola, Cladonia verticillata AND THEIR CHEMICAL CONSTITUENTS (Kajian Aktiviti Antibakteria dan Antioksidan Liken Usnea rubrotincta, Ramalina dumeticola, Cladonia verticillata dan Sebatian Kimianya)

Saranyapiriya Gunasekaran

Papers

Biological activities of four Parmotrema species of Malaysian origin and their chemical constituents

Antibacterial and Antioxidant Activity of Lichens Usnea rubrotincta, Ramalina dumeticola, Cladonia verticillata and Their Chemical Constituents

Antibacterial activity of lichen Usnea rubrotincta, Ramalina dumeticola, and Cladonia verticillata

ANTIBACTERIAL AND ANTIOXIDANT ACTIVITY OF LICHENS Usnea rubrotincta, Ramalina dumeticola, Cladonia verticillata AND THEIR CHEMICAL CONSTITUENTS (Kajian Aktiviti Antibakteria dan Antioksidan Liken Usnea rubrotincta, Ramalina dumeticola, Cladonia verticillata dan Sebatian Kimianya)

Kajian aktiviti antibakteria dan antioksidan liken Usnea rubrotincta, Ramalina dumeticola, Cladonia verticillata dan sebatian kimianya