LOW-COST METHODOLOGY FOR QUANTIFICATION OF D-LACTAM IN CAFERANA PLANT EXTRACTS

δ-Lactam (1,6-Dihydropyridin-2(3H)-one) is a heterocyclic alkaloid of six members with biological activities ranging from analgesic, antidepressant, anticholinesterase activity, anticonvulsant, neuroprotective, antiasthmatic, to anti-HIV-1, antimicrobial, and insecticidal. δ-Lactam can be the precursor material for the development of new drugs targeting neurological disorders, applied alone or concentrated in plant extracts and natural compounds. The search for novel bioactive compounds from natural sources, such as δ-lactam in caferana (Bunchosia glandulifera), requires the development of accessible analytical methods. Ultraviolet-visible (UV-Vis) spectrophotometry offers a cost-effective alternative for the quantification of several substances. This study establishes a simple method to quantify δ-lactam in caferana extracts. Given that the UV-Vis detection of δ-lactams is not widely documented, this protocol serves as a model for their preliminary quantification. The methodology is based on the Lambert-Beer Law (A=εbc), where the absorbance (A) is directly correlated to analyte concentration (c). 31 extracts samples from different caferana fractions (roots, stems, leaves, seeds, pulp, and honey) were diluted in HPLC-grade chloroform. To evaluate analyte recovery, 5 samples were enriched with a δ-lactam standard at three concentration levels. All analyses were performed in triplicate, scanning from 190 to 500 nm using 10 and 1 mm quartz cuvettes. A calibration curve was constructed using a purified δ-lactam (purity 98.4%) as a standard (0.25 to 1.0 mg/mL) previously isolated from caferana seeds. Results showed a maximum absorption wavelength (λmax) for δ lactam at 301±2 nm. The calibration curve provided the equation of the straight line mathematically with A= 742.48C (R² = 0.9987), showing linearity between the limits of quantification (LQ) of 0.255 mg/mL and 1.060 mg/mL. The molar absorptivity coefficient (ε) in chloroform was calculated as 72.64 L⋅mol−1⋅cm−1 with a 10 mm cuvette. This finding was corroborated using a 1 mm cuvette, which yielded a statistically similar result. Enriched samples demonstrated linearity with recovery values ranging from 0.030 to 0.190 mg/mL. Therefore, this study brings a fast, affordable, and accessible UV-Vis spectrophotometric method for the preliminary quantification of δ-lactam in caferana extracts. Despite the protocol is effective for initial screening, its low selectivity imposes the validation by more robust and high-resolution chromatographic techniques to rule out interferences from other compounds contained in the complex plant matrix.