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Active pharmaceutical ingredient (API)

An active pharmaceutical ingredient (API) is the substance in a drug or a pesticide that is biologically active. Besides the API, several other substances are used as an excipient (i.e. the inactive or inert substances present inside a drug). These compounds are added as diluents (add volume/mass to the drug to allow a more precise dosing for patients), additives (e.g. flavors, colours) or for pharmacokinetic considerations (e.g. facilitating drug absorption or solubility).

Anti-angiogenesis agent

These substances suppress the formation of new blood vessels, which are vital to the growth of tumours.

Aquatic environment

Rivers, lakes, ground water, sea; a broader view also includes surface run-off, effluents and sewage.

Atom economy

Atom economy (atom efficiency) defines the conversion efficacy of a chemical operation in terms of all atoms concerned (desired products produced). Atom economy can be written as: Atom economy=[(molecular mass of all desired products)/(molecular mass of all reactants)]×100

Benign by design

A concept that requires the targeted design of active pharmaceutical ingredients and adjuvants from the very beginning in order to render them readily and completely mineralized after their release into the environment.

Bio-based solvent

A fluid derived from a biomass feedstock, which is used to dissolve other chemicals without undergoing a chemical change.


The use of an enzyme or enzymes, either as a free protein(s) or as part of a whole cell system, to catalyse synthetic reactions.

Chemical substitution

Seeking to replace currently used chemicals with more benign alternatives whilst ensuring that one hazard is not being exchanged for another.

Circular economy

The application of closed loop or “cradle to cradle” strategies for the production, utilisation, recovery and reuse of products or resources.

Concerted metalation deprotonation (CMD)

A term used to describe the arrangement of the organic and acetate/carbonate groups around a palladium(ii) in the rate-determining step found in many C–H bond functionalization reactions.


Occurs when the main effects cannot be separated from the interaction effects due to the level or type of fractionation in the design (see also Interaction).

COSMO-RS: COnductor-like Screening MOdel for Real Solvents

A quantum chemistry-based equilibrium thermodynamics method that is used to accurately predict a wide range of solvent properties (solubility, vapour pressure, partition coefficient etc.).

Critical elements

Elements with significant supply risk issues that if restricted could harm a company's business or nations economy are considered to be “critical”.

Cross-coupling reaction

The reaction of two organic compounds leading to loss of two fragments and formation of one organic product. A leading example is the reaction of an organohalide (R–X) with an organoboronic acid {R′B(OH)2} to give a cross-coupled product R–R′ (containing two different organic groups—hence the term “cross-product”.

Dean–Stark water removal

Used for the continuous removal of water that is produced during chemical reaction performed at reflux temperature, in combination with a reflux condenser and a batch reactor. It was invented by E. W. Dean and D. D. Stark in 1920 for determination of the water content in petroleum.

Design of Experiments (DoE)

A structured and efficient approach to experimentation that employs statistical techniques to investigate potentially significant factors and determine their cause-and-effect relationship on the outcome of an experiment.


Integrating an awareness of the adverse effects related to the presence of pharmaceuticals in the environment into the concept of pharmacovigilance.

Elemental sustainability

Elemental sustainability is a concept whereby each element within the periodic table is guaranteed for use by both current and future generations.

Equielutropic series

A schematic showing the equivalence in polarity of different solvent mixtures.


A controllable experimental parameter that can be varied to change the reaction conditions. Factors can be continuous (i.e. variable at many settings, such as concentration, pH, temperature) or discrete (i.e. discontinuous, such as solvent, ligand, base).

Fate, degradation and transformation

Fate is the whereabouts of a chemical in the environment; it can distribute between soil, air, water, sediment and organisms; there it can be fully degraded i.e. mineralized to inorganic chemicals or only incompletely degraded (“transformed”) or accumulate in soil, water, sediment or organisms and may hereby enter the food chain.

Genotoxic impurities

DNA-reactive substances that have a potential to cause direct DNA damage and consequently require control to very tight limits in API.


The field of geopolitics traditionally studies the links between political power and geographic space (e.g. natural resources) in international relations. Industries that are dependent on products coming from a limited number of regions (such as oil or precious metals) are quite vulnerable to political tension. The policy of a regional or federal government in a certain country can therefore have a major influence on business and economics worldwide.

Heterogeneous catalysis

Refers to the form of catalysis where the phase of the catalyst differs from that of the reactants.

Heterologous expression

The use of a carrier or host organism for the production of an enzyme that does not occur naturally in that organism.

Homogeneous catalysis

There are two types of catalysts, namely heterogeneous and homogeneous catalysts. In contrast to heterogeneous, the homogeneous catalyst is in the same phase as the reactants. In general, this allows better mixing and interaction of the catalyst with the reaction mixture.

Immobilized Pd catalysts

A catalyst that has been immobilized or encapsulated by a suitable support, e.g. polymer, containing appropriate palladaphilic groups (e.g. alkenes or amides).

Immobilized Pd nanoparticles (PdNPs)

A similar definition to the immobilized Pd catalysts; the nanoparticles describe a range of higher order Pd species that are present under the reaction conditions. For example, spherical PdNPs that are ca. 2 nm in size consist of ca. 250 Pd atoms, whereas PdNPs that are ca. 4 nm in size, consist of >4000 Pd atoms.

Inherently safe

Pharmaceuticals and chemicals that have little or no hazards.


Occurs when two or more factors are dependent on each other, so that the overall result is different from what would be expected from the sum of their individual effects. Two factors interacting (A and B), results in a two factor interaction term (AB); three factors interacting gives a three factor term (ABC) etc. It is rare for three factor or higher interactions to be significant.

LD50 (lethal dose 50%)

The median lethal dose, LD50, of a toxin is the dose required to kill half the members of a tested population after specified test duration in toxicology. LD50 figures are frequently used as a general indicator of a substance's acute toxicity.

Life Cycle Assessment

A method for assessing the environmental impacts associated with all stages of a product's life, from raw material extraction right through to disposal (cradle-to-grave).

Mass-based metrics

Calculations that assess the greenness of a reaction based solely on mass inputs and outputs.

Mass intensity

A metric parameter indicating the amount of waste produced for a certain reaction/synthetic path. It is defined by the quotient of all the material that went into a certain reaction and the amount of material actually produced.


Pollutant, so-called due to the low (micro- to nano-gram per litre) concentrations in which they are found.


Full degradation of a molecule to simple compounds, such as water, carbon dioxide, ammonia and sulfate, without the formation of stable transformation products, either by organisms or non-biotic processes.

Multi parameter space

In drug discovery property space for optimisation is defined by potency, solubility, absorption, specificity, safety, metabolism and other project (indication, target) related properties.


An enzyme that has had one or more of the amino acids in the sequence changed by random or directed mutation to improve a particular catalytic parameter, such as enantiomeric excess, stability, tolerance to heat, and solvents.

One-variable-at-a-time (OVAT)

An approach to practical experimentation in which one factor is varied at a time, keeping all other factors constant. Despite its apparent logic and simplicity, it often fails to uncover the best results for a process or reaction, usually because it fails to account for the dependency between factors, aside from other reasons given in the main text (see also interaction).

Optimisation cycle

During optimisation of a compound series, researchers run through a process of hypothesis and trials. The process starts with the design and synthesis of a compound, which after biological testing in a multiparameter space leads to a verified hypothesis and design of compounds until the optimisation goal has been achieved.


In contrast to metal catalysis, the rate of a chemical reaction is increased by small organic molecules. These organocatalysts are predominantly composed of C, H, O, N, S and P and contain no metal atoms. In general, they should preferentially be insensitive to moisture or oxygen, be readily available and possess low toxicity.


An oxidant (oxidizing agent) accepts electrons from another species in an oxidation–reduction (redox) reaction. It is thus itself reduced, while the reactant in question is oxidized.


The terminology oxidase and oxygenase finds its origin in enzyme catalysis using molecular oxygen as the oxidant. In the first case, the oxidant acts as an electron acceptor and is itself reduced. In the latter case, a substrate is oxidized by transferring the oxygen atom from molecular oxygen to the substrate.


Peptides are small chains of amino acid monomers joined by peptide (amide, –CO–NH) bonds. The covalent chemical bonds are formed when the carboxyl group of one amino acid reacts with the amino group of another.

Platform molecule

Functionalised molecules (which are derived from renewable resources) used as chemical ‘building blocks’ to access a wide variety of fine chemicals.


The sum of the strength of all hydrogen bonding (specific) and other non-specific intermolecular interactions between a solute and its solvent.

Proof of concept (POC)

Demonstration of a hypothesis in a limited patient population. Achievement of POC will inform investment in the larger clinical trials required to demonstrate safety and efficacy.

Quality by Design

An approach to drug product development using a combination of risk management and scientific knowledge to understand the relationship between process parameters and unit operations to API and/or drug product critical quality attributes (CQA).


Registration, Evaluation, Authorisation and restriction of CHemicals (REACH) is the system for controlling hazardous chemicals in the European Union. It aims to provide protection to human health and the environment, and makes manufacturers and importers responsible for understanding and managing the risks of chemicals.

Reagent selection guide

A comparative ranking of the sustainability credentials of different reagents for a given transformation. They may be used to help identify alternatives to reagents whose use may be becoming increasingly restricted by legislation or company targets around reducing the use of materials of concern. They may help identify reagents/procedures that have lesser EHS implications, are more atom efficient or with fewer operational complexities, or that can be run in a more benign solvent.

Resource efficiency

Maximising the supply of products, whilst minimising waste.

SELECT criteria

An acronym describing the criteria (Safety, Environmental, Legal, Economic, Control and Throughput) against which a synthetic route can be assessed.

SIN list

The SIN (Substitute It Now!) List is a list of hazardous chemicals based on the REACH Substances of Very High Concern criteria. The list is maintained by ChemSec, (the International Chemical Secretariat) and aims to speed up the process of phasing out hazardous chemicals.

Solvent selection guide

A comparative ranking of the sustainability credentials of different solvents. Multiple categories can be viewed in detail to derive the optimum solvent for a given use, and rules can be applied to combine categories to provide generalised guidance.

Supercritical fluid

A chemical substance that is above its critical temperature and critical pressure, resulting in properties between those of a liquid and a gas.


“Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” The concept considers the impact of a process on ecological protection, society, and economic viability.

Sustainable management of water resources

Usage and protection of natural water bodies in order to not deplete quantity or quality by direct or non-direct human impact.


Unwanted effects of a chemical to humans/organisms in the environment.


Change of the chemical structure of a molecule without complete mineralization because of the formation of stable reaction products.

Waste valorization

The process of deriving value from waste, for example by extracting useful chemicals and energy.

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