Garlic peel-based carbon quantum dots as a sustainable alternative for the sensitive and green spectrofluorometric quantification of molnupiravir in pharmaceutical capsules

Abstract

Searching for natural alternatives to replace environmentally harmful chemical reagents in analysis is just as crucial as finding easily accessible analytical tools. To reinforce these concepts, this study proposes a simple spectrofluorometric approach using natural carbon quantum dots (n-CQDs) as fluorescence probes for sensitive and environmentally friendly measurement of molnupiravir, an antiviral drug that was initially developed for influenza and has demonstrated potential efficacy against COVID-19. n-CQDs were synthesized using garlic peels (GP), a waste material, via a microwave-assisted method. n-CQDs have a characteristic broad absorbance and narrow emission spectrum, making it easier to analyze several targets. The GP-based n-CQDs showed maximum excitation/emission at 265/347 nm with an acceptable quantum yield. After reaction with molnupiravir, the produced n-CQDs demonstrated unique features to determine the tested analyte. Different factors influencing the synthesis of n-CQDs and their interaction with the studied drug, molnupiravir, were investigated and optimized. Using GP-based n-CQDs as fluorescent probe for measuring molnupiravir byfluorescence (FL), a green analytical approach based on the probes' fluorescence quenching was developed (GP- n-CQDs -QN-FL). The method demonstrated good linearity from 0.5 to 30 μg/mL and detection/quantitation limits of 0.19/0.5 μg/mL. Validation studies confirmed accuracy (98-102 % recovery), precision (<2 % RSD), robustness and selectivity. Various assessment indexes have been utilized to assess the environmental friendliness and suitability aspects of the suggested approach in comparison to other existing techniques. Furthermore, n-CQDs were successfully employed for the precise analysis of molnupiravir in its pharmaceutical capsules. The comprehensive results proved that the method can be deemed eco-friendly and feasible more than the other techniques for its intended purpose for molnupiravir determination in pharmaceutical dosage forms with an average recovery 101.17 %.

Keywords: Garlic peels; Molnupiravir; Natural carbon quantum dots; Spectrofluorometry; n-CQDs.

Graphical abstract

Fig. 1

Consecutive preparation steps of natural carbon dots.

Fig. 2

A) The TEM image of the synthesized n-CQDs under a magnification power of 100 nm, B) Scanning electron microscopy images (SEM), C, D) shows a high-resolution TEM image of CQD, illustrating the crystallinity of the CQDs and shows spacing of 0.18 nm E) Zeta potential distribution of the n-CQDs, F) EDX elemental analysis of the n-CQDs.

Fig. 3

Elemental mapping illustrates the distribution of (A) carbon, oxygen, nitrogen, sulfur, and phosphorus in an overlay, followed by individual element maps: (B) carbon, (C) oxygen, (D) nitrogen, (E) sulfur, and (F) phosphorus in n-CQDs.

Fig. 4

FTIR spectrum of the synthesized n-CQDs.

Fig. 5

(A) XPS survey spectrum of n-CQD, high resolution scans of (B) C1s, and (C) O1s.

Fig. 6

The effect of diluent pH (A), mixing time (B), n-CQDs volume (C) and ionic strength (D) on the fluorescence intensity of the synthesized n-CQDs (±SD, n = 3).

Fig. 7

The fluorescence emission spectra of n-CQDs under varying concentrations of molnupiravir (0.5–30 μg/mL).

Fig. 8

Evaluation of the selectivity of n-CQDs to a wide range of metal ions and commonly used excipients in dosage form formulation (±SD, n = 3).

Fig. 9

Greenness and practicality assessments of the GP- n-CQDs-QN-FL method using different matrices such as ComplexMoGAPI, AGREEprep, and BAGI.