This a Safari Extension, it allows you so select a drug name in a web page (for example), right-click and from the dropdown menu there is the option to choose either PubChem or ChEMBL as shown below. Compound Lookup turns any compound name on a web page into a structure and a set of database identifiers, without leaving the page.

• PubChem — 2D structure, molecular formula, molecular weight and the PubChem CID

• ChEMBL — the same, with the ChEMBL ID

• ID lookup — the compound’s identifier in ChEMBL, DrugBank, PDB, SureChEMBL and PubChem at once, together with its InChIKey

If you then choose for example PubChem the structure (the image is from PubChem) is displayed (plus other matches) on a card beside your selection, and a link to the PubChem record via the CID, which opens in a new browser window.

Alternatively if you choose the ChEMBL option the structure is shown with a link to the ChEMBL record via the ChEMBL ID together with any other matches.

The ID Lookup option uses UniChem (https://www.ebi.ac.uk/unichem/)

UniChem is large-scale non-redundant database of pointers between chemical structures and EMBL-EBI chemistry resources. Its purpose is to optimise the efficiency with which structure-based hyperlinks may be built and maintained between chemistry-based resources, and is particularly suitable for creating such links ‘on the fly’ (by use of REST web services).

The plugin first searches PubChem to get the structure and the InChiKey, InChIKeys are a hashed version of a full InChI used to facilitate speedier searching. The plugin uses the InChiKey to search UniChem to provide a list of identifiers and links to the appropriate

Compound Lookup for Safari – installation

1. Download and Unzip this archive and drag “Compound Lookup.app” into your Applications folder.
   It needs to stay there: Safari loads the extension from the app.
2. Open “Compound Lookup.app” once. A small window appears – that’s all it does.
   It is signed and notarised by Apple, so it opens without a security warning.
3. In Safari: Settings > Extensions, and tick “Compound Lookup”.
4. The first time you use it, Safari asks whether the extension may access websites.
   Allow it. It needs PubChem (pubchem.ncbi.nlm.nih.gov) and EMBL-EBI (www.ebi.ac.uk)
   to look compounds up, plus the page you’re reading to show the result card.
   You can change this later under Settings > Extensions > Compound Lookup.

A few notes

Selections are cleaned up as you’d expect, so a name grabbed mid-sentence with a trailing full stop or wrapping quotes still resolves — while names that genuinely contain punctuation, such as (R)-ibuprofen, 2,4-D and N,N-dimethylformamide, are left intact. Only the text you select, and only to the database you picked from the menu is sent. This only works for html pages not displayed pdf.

The card says which kind of match you got. A weak one is labelled “uncertain” with a link to the database’s own search. In ID lookup, a source that holds only a close relative is flagged — ibuprofen’s PDB entry is marked “different stereochemistry”, because the PDB holds the single enantiomers rather than the racemate — and a source holding nothing says so, because absence is informative too.

Compound data and structure images come from PubChem (NIH/NLM/NCBI), ChEMBL (EMBL-EBI) and UniChem (EMBL-EBI), through their public APIs. This extension is an independent tool and is not affiliated with, or endorsed by, any of those organisations.