Lignin, a phenolic polymer in the secondary wall, is the major cause of lignocellulosic biomass recalcitrance to efficient industrial processing. From an applications perspective, it is desirable that second-generation bioenergy crops have lignin that is readily degraded by chemical pretreatments but still fulfill its biological role in plants. Because plants can tolerate large variations in lignin composition, often without apparent adverse effects, substitution of some fraction of the traditional monolignols by alternative monomers through genetic engineering is a promising strategy to tailor lignin in bioenergy crops. However, successful engineering of lignin incorporating alternative monomers requires knowledge about phenolic metabolism in plants and about the coupling properties of these alternative monomers. Here, we review the current knowledge about lignin biosynthesis and the pathways towards the main phenolic classes. In addition, the minimal requirements are defined for molecules that, upon incorporation into the lignin polymer, make the latter more susceptible to biomass pretreatment. Numerous metabolites made by plants meet these requirements, and several have already been tested as monolignol substitutes in biomimetic systems. Finally, the status of detection and identification of compounds by phenolic profiling is discussed, as phenolic profiling serves in pathway elucidation and for the detection of incorporation of alternative lignin monomers.

/pdf/metabolic-engineering-of-novel-lignin-in-biomass-crops-4emnnx1bxv.pdf

Metabolic engineering of novel lignin in biomass crops

https://www.arca.fiocruz.br/bitstream/icict/25943/2/Bezerra%20DP%20Overview%20of%20the%20therapeutic....pdf

Overview of the therapeutic potential of piplartine (piperlongumine).

Lignans of sesame: purification methods, biological activities and biosynthesis--a review.

Schistosoma mansoni: In vitro schistosomicidal activity of piplartine

Infectious diseases caused by parasites are a major threat for the entire mankind, especially in the tropics More than 1 billion people world-wide are directly exposed to tropical parasites such as the causative agents of trypanosomiasis, leishmaniasis, schistosomiasis, lymphatic filariasis and onchocerciasis, which represent a major health problem, particularly in impecunious areas Unlike most antibiotics, there is no “general” antiparasitic drug available Here, the selection of antiparasitic drugs varies between different organisms Some of the currently available drugs are chemically de novo synthesized, however, the majority of drugs are derived from natural sources such as plants which have subsequently been chemically modified to warrant higher potency against these human pathogens In this review article we will provide an overview of the current status of plant derived pharmaceuticals and their chemical modifications to target parasite-specific peculiarities in order to interfere with their proliferation in the human host

https://www.mdpi.com/1422-0067/14/2/3395/pdf

Natural Products as a Source for Treating Neglected Parasitic Diseases

The n-hexane, ethyl acetate, methanol, and acetone extracts of Piper cubeba Linn. and P. retrofractum Vahl. (Piperaceae) were evaluated in vitro against promastigotes of Leishmania donovani, and all exhibited significant in vitro activity at 100 μg/ml. Two lignans, cubebin and hinokinin, were isolated from the hexane extract of P. cubeba; and one bis-epoxy lignan, (−)-sesamin, and two amides, pellitorine and piplartine, were isolated from the hexane and methanol extracts of P. retrofractum. Cubebin and piplartine showed significant antileishmanial activity in vitro at 100 μM and were further tested in vivo in a hamster model of visceral leishmaniasis. Piplartine showed activity at 30 mg/kg dose. This is the first report of antileishmanial activity of these two plants and their isolated constituents.

Antileishmanial amides and lignans from Piper cubeba and Piper retrofractum

Hexane, chloroform and ethyl acetate extracts (100 microg/ml) of Alpinia galanga rhizomes exhibited significant activity in vitro against promastigotes of L. donovani. Twelve compounds namely, methyleugenol (1), p-coumaryl diacetate (2), 1'-acetoxychavicol acetate (3), 1'-acetoxyeugenol acetate (4), trans-p-acetoxycinnamyl alcohol (5), trans-3,4-dimethoxycinnamyl alcohol (6), p-hydroxybenzaldehyde (7), p-hydroxycinnamaldehyde (8), trans-p-coumaryl alcohol (9), galangin (10), trans-p-coumaric acid (11) and galanganol B (12) were isolated from these extracts. Of these, compounds 2, 3, 4 and 5 were found most active in vitro against promastigotes of L. donovani with IC50 values of 39.3, 32.9, 18.9 and 79.9 microM respectively. This is the first report of antileishmanial activity of the extracts and isolated constituents of A. galanga.

http://nopr.niscair.res.in/bitstream/123456789/7407/1/IJEB%2048%283%29%20314-317.pdf

Ranvir Singh

Papers

Antileishmanial amides and lignans from Piper cubeba and Piper retrofractum

Antileishmanial phenylpropanoids from Alpinia galanga (Linn.) Willd.