Lipidomic Profiling of Commercial Hydnocarpus wightianus Oil by UPLC-QTOF-MS/MS and GC-MS: Degradation-Associated Lipid Classes as Candidate Quality Attributes for a Non-Pharmacopoeial Excipient

Background/Objectives: Chaulmoogra oil (ChO), from Hydnocarpus wightianus Blume seeds, is returning to use as the lipid phase of transdermal carriers, yet no pharmacopoeial monograph governs it. This work asked whether lipid classes associated with hydrolysis and oxidation distinguish oils that a fatty acid specification would not separate. Methods: Three commercial products, each analyzed once, were profiled by ultra-performance liquid chromatography with quadrupole time-of-flight tandem mass spectrometry (UPLC-QTOF-MS/MS), and two of them also by gas chromatography-mass spectrometry (GC-MS). Growth inhibition was tested by broth dilution. Results: Cyclopentenyl acids dominated the fatty acid composition. In one product (ChO 2), fatty acyl esters of hydroxy fatty acids (FAHFA) accounted for about 14% of the annotated negative-mode signal, against 2 and 4% in the others, and diacylglycerols for 1.3% of the positive-mode signal, against 0.3 and 0.7%. The acid value (1.9 to 2.8 mg KOH/g) and the share of oxidized triacylglycerols were instead highest in ChO 3. No measurable growth inhibition of Escherichia coli, Bacillus cereus or Candida albicans by the crude oils was detected up to 250 µg/mL. Conclusions: A specification based on fatty acid composition alone would not separate these products, and the FAHFA and diacylglycerol shares are proposed as candidate attributes associated with hydrolysis and oxidation that require validation.