Natural plant extracts as an economical and ecofriendly alternative for harvesting microalgae.

The study investigated the ability of plant based natural coagulants from Azadirachta indica; Ficus indica; Moringa oleifera; Citrus sinensis; Punica granatum and Musa acuminata to harvest the microalgal biomass. Influence of eluent type (water and NaCl) and concentration (1-5 N) on coagulant extraction; coagulant dosage (1-5 g) and volume (20-100 ml); pH (6-12) and algal concentration (0.1-1 g l-1) on harvesting were analyzed. The results obtained were compared with alum and chitosan. FTIR and biochemical analysis confirmed the presence of bioactive compounds to aid coagulation. Biomass removal efficiency of 75.50% was obtained with M. oleifera extracts (8 mg ml-1) at pH 7.5-7.8, within 100 min. The harvesting efficiency increased to 95.76% when 4 mg ml-1M. oleifera extracts was combined with 0.75 mg ml-1 chitosan. The life cycle and cost analysis acknowledged the eco-friendly coagulants as strong alternative for conventional coagulants used in microalgal harvesting, thereby improvising the overall bioprocess.

Botanical and biological pesticides elicit a similar Induced Systemic Response in tomato (Solanum lycopersicum) secondary metabolism.

Natural pesticides have attracted substantial interest due to the increase in organic agriculture and enhanced attention to environmental pollution. Plant Growth Promoting Bacteria (PGPB) are applied for both disease control and growth enhancement; PGPBs are known to elicit Induced Systemic Response (ISR) in plants. However, less is known about the effect of botanical pesticides, such as the azadirachtin-containing neem extracts, on plant metabolism. This study aimed to investigate the effects of foliar application of the above-mentioned natural pesticides on the metabolic profiling of tomato. Leaf application of Bacillus subtilis fostered Induced Systemic Resistance (ISR) in treated plants via the Jasmonic acid pathway, and enhanced production of secondary metabolites such as flavonoids, phytoalexins and auxins. Changes in sterols and terpenes, as well as an increase in glucosinolates were also observed. Interestingly, azadirachtin-treated tomatoes also showed an increase in ISR and our results revealed that most of the enriched metabolites are shared with a B. subtilis treatment, suggesting conserved biochemical responses. These (un)expected findings indicate that plants are not insensitive to application of natural pesticide and while Azadirachtin is applied as a direct pesticide, it also stimulates a defense response in tomatoes very similar to B. subtilis induced ISR.

Morphological and biochemical changes in Azadirachta indica from coal combustion fly ash dumping site from a thermal power plant in Delhi, India.

The foliar and biochemical traits of Azadirachta indica A. Juss from fly ash (FA) dumping site in Badarpur thermal power plant (BTPP) New Delhi, India was studied. Three different experimental sites were selected at different distances from the thermal power plant. Ambient suspended particulate matter (SPM) and plant responses such as leaf pigments (chlorophyll a, chlorophyll b, and carotenoids), total chlorophyll, net photosynthetic rate, stomatal index (SI), stomatal conductance (SC), intercellular carbon dioxide concentration [CO2]i, net photosynthetic rate (NPR), nitrogen, nitrate, nitrate reductase activity, proline, protein, reducing sugar and sulphur content were measured. Considerable reduction in pigments (chlorophyll a, chlorophyll b and carotenoids), and total chlorophyll was observed at fly ash dumping site. Fly ash stress revealed the inhibitory effect on Nitrate reductase activity (NRA), Nitrate, soluble protein, and reducing sugar content, whereas stimulatory effect was found for the stomatal index, nitrogen, proline, antioxidants and sulphur content in the leaves. Under fly ash stress, stomatal conductance was low, leading to declining in photosynthetic rate and increase in the internal CO2 concentration of leaf. Single leaf area (SLA), leaf length and leaf width also showed a declining trend from control to the polluted site. Antioxidant enzymes increased in leaves reflecting stress and extenuation of reactive oxygen species (ROS).

Effect of elicitors and precursors on azadirachtin production in hairy root culture of Azadirachta indica.

The present study involved strategies for enhancement in in vitro azadirachtin (commercially used biopesticide) production by hairy root cultivation of Azadirachta indica. Improvement in the azadirachtin production via triggering its biosynthetic pathway in plant cells was carried out by the exogenous addition of precursors and elicitors in the growth medium. Among the different abiotic stress inducers (Ag(+), Hg(+2), Co(+2), Cu(+2)) and signal molecules (methyl jasmonate and salicylic acid) tested, salicylic acid at 15 mg l(-1) of concentration was found to enhance the azadirachtin yield in the hairy roots to the maximum (up to 4.95 mg g(-1)). Similarly, among the different biotic elicitors tested (filter-sterilized fungal culture filtrates of Phoma herbarium, Alternaria alternata, Myrothecium sp., Fusarium solani, Curvularia lunata, and Sclerotium rolfsii; yeast extract; and yeast extract carbohydrate fraction), addition of filter-sterilized fungal culture filtrate of C. lunata (1 % v/v) resulted in maximum azadirachtin yield enhancement in hairy root biomass (up to 7.1 mg g(-1)) with respect to the control (3.3 mg g(-1)). Among all the biosynthetic precursors studied (sodium acetate, cholesterol, squalene, isopentynyl pyrophosphate, mavalonic acid lactone, and geranyl pyrophosphate), the overall azadirachtin production (70.42 mg l(-1) in 25 days) was found to be the highest with cholesterol (50 mg l(-1)) addition as an indirect precursor in the medium.

Role of chloroplastidial proteases in leaf senescence.

In this report the effect of hydrogen peroxide (H2O2) on peroxidase (POD) activity during leaf senescence was studied with and without phenylmethylsulfonyl fluoride (PMSF) pre-treatment in detached neem (Azadirachta indica A. juss) leaf chloroplasts. Increased POD activity was detected in natural and H2O2-promoted senescent leaf chloroplasts compared to untreated control mature green leaf chloroplasts. However, under H2O2 POD activity markedly increased at 1 day, and then significantly decreased until 4 days. In the presence of H2O2, PMSF, the induction of POD activity was alleviated at 1 day, whereas reduced after 4 days. In contrast, in the presence of H2O2, cycloheximide (CX), the induction of POD activity was reduced at 1 day, whereas alleviated after 4 days. The was a partial reduction in H2O2-induced POD activity with PMSF and CX, indicating the presence of pre-existing inactive PODs in chloroplasts. We also propose a new role for chloroplastidial proteases as activators of pre-existing inactive PODs during leaf senescence.

Increased production of azadirachtin from an improved method of androgenic cultures of a medicinal tree Azadirachta indica A. Juss.

Present report is the first direct evidence of azadirachtin production in androgenic haploid cultures of Azadirachta indica, a woody medicinal tree. Anther cultures at early-late-uninucleate stage of microspores were established on MS medium with BAP (5 µM), 2,4-D (1 µM) and NAA (1 µM) containing 12% sucrose. The calli, induced, were further multiplied on 2,4-D and Kinetin media. Shoots, differentiated on BAP (2.2 µM) + NAA (0.05 µM) medium, were elongated on MS + BAP (0.5 µM) and multiplied on MS + BAP (1 µM) + CH (250 mg/l). Thereafter, the shoots were rooted on » MS + IBA (0.5 µM). Cytological analysis of the calli and regenerants have confirmed their haploid status with the chromosome number as 2n = x = 12. The haploid cell lines and leaves from in vitro grown plantlets were analyzed for azadirachtin by RP-HPLC and mass spectroscopy. Maximum azadirachtin (728.41 µg/g DW) was detected in calli supporting best shoot proliferation while least (49 µg/g DW) was observed in an undifferentiated line from maintenance medium. This study has brought us a step closer to develop genetically pure lines that could serve as new and attractive alternative ways of homogeneous controlled production of high value compounds, round the year, independent of geographical and climatic barrier.

Biochemical changes in plant leaves as a biomarker of pollution due to anthropogenic activity.

The air pollution due to anthropogenic activities seriously affected human life, vegetation, and heritage as well. The vegetation cover in and around the city mitigates the air pollution by acting as a sink for pollution. An attempt was made to evaluate biochemical changes occurred in four selected plant species, namely Azadirachta indica, Mangifera indica, Delonix regia, and Cassia fistula of residential, commercial, and industrial areas of Nagpur city in India. It was observed that the correlated values of air pollutants and plant leaves characteristics alter foliar biochemical features (i.e., chlorophyll and ascorbic acid content, pH and relative water content) of plants due to air pollution. The changes in air pollution tolerance index of plants was also estimated which revealed that these plants can be used as a biomarker of air pollution.

Comparative repellent activities of some plant extracts against Simulium damnosum complex.

The root and leaf extracts of four plants, Occimum gratissimum, Azadirachta indica, Pterocarpus santalinoides, and Pistia hyptis, were studied for repellent activities against the adults of Simulium damnosum sensu lato. The leaves and roots were extracted with 95% ethanol and the stocks were diluted with paraffin. The repellent activities of the extracts were investigated using human baits along the banks of River Oyan and River Ogun in southwestern Nigeria. The results showed that the root extract of O. grattissium and leaf extract of P. hyptis had highest repellent potentials with 78% and 78.1% protection against S. damnosum sensu lato, respectively, whereas the root and leaf of P. santalinoides recorded the least. Although there were significant differences in the percentage of protection of the extracts of the plants (p < 0.05), the variations in the percentage of protection of the leaf and root extracts were not statistically significant (p > 0.05). The study concludes that there exist some repellent efficacies in the extracts of the plants, most importantly O. grattissimum and P. hyptis. The plant extracts can further be developed in the prevention of man-vector contact in onchocerciasis endemic communities.

Antimicrobial activities of skincare preparations from plant extracts.

In this study, Tithonia diversifolia Helms. (A Gray), Aloe secundiflora (Miller) and Azadirachta indica (A. Juss) plant extracts were used to make herbal soaps while Thevetia peruviana (Schum) seed oil was used to make a herbal lotion for skincare. The soaps were tested for the growth inhibition of Escherichia coli, and Candida albicans. The lotion was evaluated against Staphylococcus aureus and E.coli. Although Tithonia diversifolia soap exhibited the highest inhibitory effect on the test bacterial strains, it had the least inhibition against C. albicans. Results from this study indicated that the 'Tithonia diversifolia' soap would have superior skin protection against the tested bacteria but would offer the least skin protection against C. albicans. The herbal lotion inhibited S. aureus and E. coli in a concentration dependent manner, however, the inhibitory effect was more pronounced on S. aureus.

Direct differentiation of somatic embryos on different regions of intact seedlings of Azadirachta in response to thidiazuron.

Direct differentiation of somatic embryos occurs in high-frequency and at high density in response to 1.0 microM TDZ, on different regions-hypocotyl, epicotyl, cotyledonary-node, cotyledons and leaves-of intact seedlings of Azadirachta. One-week-old seedlings on this medium exhibited stress symptoms as visible by the loss of root formation and reduction in the elongation of hypocotyl and epicotyl. Globular somatic embryos were more abundant on hypocotyl, epicotyl, stem tip and leaves. The arrest of embryos at this stage was possibly due to their presence in high density. Well-developed somatic embryos were present on the cotyledons and the cotyledonary-node. These embryos on isolation and transfer to hormone-free medium regenerated readily to form plantlets. The possible role of stress in thidiazuron-induced somatic embryo formation is discussed.

Production of haploids of neem (Azadirachta indica A. Juss.) by anther culture.

Androgenic haploids of the neem tree (Azadirachta indica A. Juss.) were produced by anther culture at the early- to late-uninucleate stage of pollen. Haploid formation occurred via callusing. The best medium for inducing callusing in the anther cultures was Murashige and Skoog's basal medium (MS) (9% sucrose) supplemented with 1 microM 2,4-D, 1 microM NAA and 5 microM BAP, while anther callus multiplied best on MS medium supplemented with 1 microM 2,4-D and 10 microM Kn. These calli differentiated shoots when transferred to a medium containing BAP; 5 microM BAP was optimum for young calli (75% cultures differentiated shoots), but older calli showed the best regeneration with 7.5 microM BAP. Shoots elongated at a lower concentration of BAP-0.5 microM. These shoots were multiplied by forced axillary branching and rooted in vitro. The plants were subsequently established in soil. Of the plants that regenerated from anther callus 60% were haploid, 20% were diploid and 20% were aneuploid.