Recognition of antitussive components in Farfarae Flos based on grey relational analysis and partial least squares regression.

Objectives: Farfarae Flos has the effect of cough suppression and phlegm elimination, with cough suppression as the main function. Studies have revealed that certain components of Farfarae Flos may be related to its cough suppressant effect, and some components have been confirmed to have cough suppressant activity. However, the antitussive material basis of Farfarae Flos has not been systematically elucidated. This study aims to elucidate the group of active ingredients in Farfarae Flos with cough suppressant activity by correlating the high performance liquid chromatography (HPLC) fingerprint of Farfarae Flos extract with its cough suppressant activity.

Methods: HPLC was used to establish the fingerprint profiles of 10 batches of Farfarae Flos extract and obtain their chemical composition data. Guinea pigs were selected as experimental animals and the citric acid-induced cough model was used to evaluate the antitussive efficacy data of 10 batches of Farfarae Flos extract. SPF-grade healthy male Hartley guinea pigs were randomly divided into the S1 to S10 groups, a positive control group, and a blank control group (12 groups in total), with 10 guinea pigs in each group. The S1 to S10 groups were respectively administered Farfarae Flos extract S1 to S10 (4 g/kg), the positive control group was administered pentoverine citrate (10 mg/kg), and the blank control group was administered purified water. Each group received continuous oral administration for 5 days. The guinea pigs were placed in 5 L closed wide-mouth bottles, and 17.5% citric acid was sprayed into the bottle with an ultrasonic atomizer at the maximum spray intensity for 0.5 minutes. The cough latency period and cough frequency in 5 minutes were recorded for each guinea pig. Grey relational analysis (GRA) and partial least squares regression (PLSR) were used to conduct spectral-effect correlation analysis of the chemical composition data of Farfarae Flos extract and the antitussive efficacy data, and predict the group of active ingredients in Farfarae Flos with antitussive activity. The bioequivalence verification was conducted to verify the predicted group of active ingredients in Farfarae Flos with antitussive activity: SPF-grade healthy male Hartley guinea pigs were randomly divided into a S9 group, an active ingredient group, a positive control group, and a blank control group (4 groups in total), with 10 guinea pigs in each group. The S9 group was administered Farfarae Flos extract S9 (4 g/kg), the active ingredient group was administered the predicted combination of antitussive active ingredients (dose equivalent to 4 g/kg of Farfarae Flos extract S9), the positive control group was administered pentoverine citrate (10 mg/kg), and the blank control group was administered purified water. Each group received continuous oral administration for 5 days, and animal modeling and observation of efficacy indicators were the same as above.

Results: The HPLC fingerprint of 10 batches of Farfarae Flos extract was established, and the peak area data of 14 main common peaks were obtained. The antitussive effect data of 10 batches of Farfarae Flos extract were obtained. Compared with the blank control group, the cough latence in the positive control group and S1, S2, S3, S4, S6, S7, S8, S9, S10 groups was prolonged (all <0.01), while the cough frequency in 5 minutes in the positive control group and S1, S2, S4, S6, S8, S9, S10 groups was decreased (all <0.05). The analysis of spectrum-effect relationship revealed that isochlorogenic acid C, isochlorogenic acid A, chlorogenic acid, isochlorogenic acid B, isoquercitrin, and rutin had high contribution to the antitussive effect of Farfarae Flos, and the 6 components were predicted to be the antitussive component group of Farfarae Flos. The verification of bioequivalence showed that there were no statistically significant differences in the antitussive effect between the S9 group and the antitussive component composition group(all 0.05), which confirmed that isochlorogenic acid C, isochlorogenic acid A, chlorogenic acid, isochlorogenic acid B, isoquercetin, and rutin were the antitussive component group of Farfarae Flos.

Conclusions: The analysis of spectrum-effect relationship combined with the verification of bioequivalence could be used to study the antitussive material basis of Farfarae Flos. The antitussive effect of Farfarae Flos is the result of the joint action of many components.