The term ‘alkaloids’ may be unfamiliar to most of us but if I start naming some examples which fall into this group of ‘nitrogenous bases secondary metabolites’, you will know what I mean. 
Some of the big names include morphine, quinine, strychnine, nicotine etc. basically a continuous list of –ine’s. The thing to note is that though the alkaloids were attributed to pharmacologically active bases derived from plants however, animals (including us!), insects and microbes also produce them.
Narrower definitions state the nitrogen atom(s) within the compound must be in a negative oxidation state or are also known as ‘Imperfect alkaloids’, ‘
Pseudoalkaloid’ and ‘Protoalkaloid’. Though certain alkaloids are notoriously famous for being wrongly used for recreational purposes, it is important to remember that this was only in recent years. For centuries and for some, even thousands of years alkaloids were used as medicine.
Between 1803-1805, Friedrich Sterurner first isolated the morphine we all know (and perhaps love) from around 20 alkaloid substances in raw opium. An astonishing feat for an apothecary’s assistant but unfortunately the chemistry was poorly understood at the time as its basic structure was only found over a
century later. Nevertheless, people soon hailed the opiate as a panacea and sold as an over-the-counter miracle, until its later overriding addictive qualities. Due to its high yield of around 10%, morphine is able to be isolated in large quantities to satisfy the increasing demand to relieve both severe chronic and labour pain, quadrupling only in the last two decades.
- Codenine
In reality most of the isolated class A drug is converted into its (I guess more friendly) class B cousin, codeine used in conjunction with paracetamol for moderate pain. A simple change of one hydroxyl group to a methoxide groups is all that is needed. Aside from high potency, when it comes to analgesic properties morphine is at the top of its game, blocking the nerve cell receptor site to eliminate pain (similar to our own endorphins) all the while allowing a constant state of consciousness. Like an enzyme and substrate, the morphine locks onto the receptor active site blocking all pain signals. It is the precise shape of the molecule which makes it so effective. Recreational uses of morphine explore the property of detachment one feels from the world which evokes pleasure. Just as the caffeine (another psychoactive drug btw) we consume, forever increasing concentrations of morphine are also required for the same effect. This makes addiction spiral out of control in a deadly cycle.
Diamorphine, commonly known as heroin was first isolated from morphine in 1874. Ironically it was first intended as a cure for morphine addiction. This later causes common heroine abuses and addiction. The heroine is less soluble in water but more soluble in non-polar solvents causing the requirement to be injected. It is more potent than morphine in terms of passing rapidly through the bloodstream preventing passage of larger, water-soluble molecules.
Lastly a completely synthetic molecule, the opioid methadone hydrochloride which I witness being dispersed during my own work experience placement. Though it has some analgesic properties it is now primarily used as a substitute drug to combat addiction which along with other substitutes cost the NHS £3.6 billion each year. This is really a grey area, with some physicians protesting that is even harder to ease off than other recreational drugs.
Author – Jiangmin Hou
Jiangmin is a 5th year high school student currently studying five STEM subjects at Scottish Higher level-Mathematics, Physics, Biology, Computer Science and Chemistry. She is interested in pursuing a degree in Medicine after completion of Secondary Education.
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