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Hunter Young
Hunter Young


In this article I would like to survey the books that contain information on the performance of microchemical tests, including spot testing; illustrations and/or annotations are offered for each reference. The presentation will be more or less chronological so that the history of the entire branch of this microscopical science will be apparent. We will start with some definitions, and set boundaries.



Benzylisoquinoline alkaloids (BIAs) constitute a family of major secondary metabolites of plants, of which many members, such as morphine and codeine, exhibit strong pharmaceutical effects. Similar to other natural compounds, unknown and scarce BIAs are expected to be a source for drug discovery; BIAs with novel functions have been demonstrated as promising anticancer drug candidates, including novel bisbenzylisoquinoline alkaloids used as ingredients for crude drugs4,5. Because most BIAs are synthesised via (S)-reticuline6, various BIAs can be produced if enough (S)-reticuline is available; however, (S)-reticuline is an intermediate that can be easily converted to other BIAs in plants and does not accumulate in sufficient levels. Additionally, it is difficult to purify (S)-reticuline from natural resources, such as the latex of opium poppies, without contamination of other BIAs possessing similar chemical properties. Furthermore, inexpensive synthesis of (S)-reticuline by chemical methods is also difficult because of the requirements for troublesome regiospecific and chiral-specific reactions.

Sulphate conjugation often changes the solubility of compounds and is involved in the detoxification of harmful compounds. However, in this study, sulphate conjugation changed the biological effects of (S)-reticuline, suggesting that sulphate conjugation is one of the methods necessary for the synthesis of novel non-natural BIAs, thereby extending the spectrum of biological effects. We found that hSULTs exhibited significant activities on other BIAs, including (R,S)-norlaudanosoline and (S)-scoulerine (Supplementary Table S2). Furthermore, some flavonoids, such as naringenin and quercetin, were also significantly sulphated (Supplementary Table S2). This wide spectrum of hSULT substrate specificity would facilitate the production of various sulphate-conjugated plant secondary metabolites. In principle, this concept could be applied to other conjugations, such as acetylation, methylation, and glycosylation, using appropriate enzymes. These conjugations could also be applied to other BIA subfamilies, such as protoberberine and morphinan alkaloids. The protoberberine skeleton can be produced from (S)-reticuline by the addition of the berberine bridge enzyme to a bacterial (S)-reticuline-production system, as demonstrated in yeast systems27,28,29. Morphinan alkaloids have also been produced by engineered E. coli10 and yeast11 strains. By combining BIA skeletons with various conjugated groups, an enormous range of non-natural BIAs can be produced as derivatives of natural BIAs, which can further extend the diversity in biological activities.

In the pharmaceutical and food industries, several synthetic or natural antioxidants have been used to prevent oxidation and peroxidation processes [217]. As synthetic antioxidants have been shown to have side effects, natural antioxidants are sought after [218]. Recently, the exploration of natural antioxidants for nutraceuticals and pharmaceuticals industries has increased. Researchers are looking for antioxidants from natural sources, such as medicinal plants. Because of their huge potential for producing biologically active natural products, microalgae are one of the richest and most economical sources of natural compounds with strong antioxidants effects [219]. The antioxidant potential of these substances has been determined by various methods, including ABTS, DPPH radicals scavenging assay, ferric reducing potential, and metals chelating essays. Structural features such as a phytyl chain, a porphyrin ring, and conjugated double bonds are responsible for the antioxidant qualities [220]. Chlorophyll a and its metabolites produced by microalgae species are reported to have antioxidant activities [221]. as do most of the pigment metabolites of microalgae. The pigment fucoxanthin and its derivatives, such as auroxanthin, isolated from the microalga Undaria pinnatifida, have strong radical scavenging action [222]. Fucoxanthin is reported to have higher antioxidant effects than β-Carotene in tests of rat liver and plasma [223, 224]. The chemical structure of fucoxanthin shows two hydroxyl groups in a ring structure, which are considered the active moiety for free radical scavenging [225]. Phycobiliproteins (e.g., C-phycocyanin, R-phycoerythrin) are commercially used in the food and cosmetic industries as natural dyes [226]. Phycoerythrobilin, produced by some species of microalgae, has been shown to possess antioxidant activity [227]. Hence, the widespread existence of natural products with strong antioxidant activity increases the economical and nutritional potential of microalgae for the food, pharmaceutical, and nutraceutical industries.

An ideal microanalytical method for forensic drug analysis would be inexpensive, fast, automated and suitable for all known drugs; however, no such tool currently exists. Traditional light microscopy and microcrystal tests have been used together for more than 100 years, and are proven useful when automated instrumental analysis is unavailable or not appropriate, if mixtures of one or more drugs, excipients, diluents or adulterants are present, or when the drug is held in alternative delivery devices such as gels or transdermal patches. Furthermore, while some crime laboratories may lack certain automated instrumental capabilities, most have light microscopes and properly trained microscopists. Microcrystal tests, using polarized light microscopy (PLM), can identify most illicit drugs specifically and quickly (usually within a few minutes), and they are inexpensive compared to other methods. In addition, proper use of the light microscope and microcrystal tests can check and confirm the results obtained by alternative methods. It is envisaged that this compendium will fulfill a critical need for reliable analytical methods and assist forensic scientists and other researchers in their work.

In the class of phytochemicals, alkaloids have been promising anticancer agents. The alkaloids represent a highly diverse group of compounds, around 3000 distinct alkaloids have been characterized from plants, fungus, and animals together [20]. Some of the commonly known alkaloids include Morphine and Nicotine [21]. The alkaloids are low molecular weight organic nitrogenous compounds, often chemically classified into pyrrolidines, pyridines, tropanes, pyrrolizidines, isoquinolines, indoles, quinolines, and terpenoids and steroids. Generally, the alkaloids are colourless, crystalline, and non-volatile ( ) and are reported as low in toxicity, with higher stability. It has been found that alkaloids impart a restraining effect on the topoisomerase enzyme, thus stalling DNA replication and cell death [22]. Therefore, alkaloids have been a base for drug development for various ailments such as anti-inflammatory, antibacterial, and antitumor [23]. The plant-based alkaloids have proven efficacy in oncogenesis suppression.

The next advancement in the detection of poisons came in 1850 when a valid method for detecting vegetable alkaloids in human tissue was created by chemist Jean Stas.[14] Stas's method was quickly adopted and used successfully in court to convict Count Hippolyte Visart de Bocarmé of murdering his brother-in-law by nicotine poisoning.[14] Stas was able to successfully isolate the alkaloid from the organs of the victim. Stas's protocol was subsequently altered to incorporate tests for caffeine, quinine, morphine, strychnine, atropine, and opium.[15]

Alumina (aluminum oxide) is a strong polar adsorbent used in the separation of natural products especially in the separation of alkaloids. The strong positive field of Al3+ and the basic sites in alumina affecting easily polarized compounds lead to the adsorption on alumina that is different from that on silica gel. The application of alumina in the separation of natural products has decreased significantly in recent years because it can catalyze dehydration, decomposition or isomerization during separation. Zhang and Su reported a chromatographic protocol using basic alumina to separate taxol (74, Fig. 11) from the extract of Taxus cuspidate callus cultures and found the recovery of taxol was more than 160%. They found that the increase of taxol came from the isomerization of 7-epi-taxol (75) catalyzed by alumina. It was also found that a small amount of taxol could be decomposed to baccatin III (76) and 10-deacetylbaccatin III (77) in the alumina column [49]. Further investigation into the separation of taxol on acidic, neutral and basic alumina indicated that the Lewis souci and the basic activity cores on the surface of alumina induced the isomerization of 7-epi-taxol to taxol [50].

In the phytochemical screening of this study, the methanol extract of H. micranthus showed positive indication for the presence of alkaloids, flavonoids, saponins, tannins, steroids, phenols, diterpines and anthraquinones. Therefore, the observed antibacterial activity of the methanol extract can be attributed primarily by the nature of biologically active components of the plant like alkaloids, diterpines, tannins, saponins, phenols, flavonoids and steroids which are well known for their antimicrobial activity [6, 44] supporting the traditional use of the plant and secondarily by the stronger extraction capacity of methanol could have produced a large number of active constituents responsible for antibacterial activity [8, 42]. Expected mode of antimicrobial action of some secondary metabolites may be related for example tannins inactivate microbial adhesins, enzymes and cell envelope transport proteins; flavonoids targeted on microbial membrane; alkaloids intercalate in to cell wall and /or Deoxyribonucleic acid (DNA) where as diterpines and phenolic substances disrupt microbial membrane [47]. These secondary compounds may come into play either individually or synergistically to confer the antibacterial potential of this plant. 041b061a72


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