Cordia verbenacea, DC.

Fortes, Carlos Herminio Magalhães, Ferrari, Fabiola Tonelli, Baldisserotto, Bernardo, Schmidt, Denise, Sutili, Fabrício Jaques & Heiznmann, Berta Maria, 2024, Anesthetic potential of essential oils from Brazilian native plants in Rhamdia quelen juveniles (silver catfish), Neotropical Ichthyology 22 (3), pp. e 240034-e 240034 : e240034-240034

Cordia verbenacea leaves essential oil (CVOl).

An inversely proportional relationship was observed between CVOl concentration and induction time to reach S2, which was achieved for all concentrations studied. Stages S3a and S3b were not reached within 30 min in fish exposed to 50 and 80 mg L- 1, and at higher concentrations there was no difference between them. The S4 stage was induced between 200 to 400 mg L- 1, also without differences between concentrations. The recovery times between the two lowest concentrations evaluated did not differ from each other and were below 20 min, while the fish subjected to concentrations of 100 to 400 mg L- 1 did not recover within the maximum observation period ( Tab. 4 ).

Essential oil from leaves of Cordia verbenacea (CVOl).

The fish subjected to 50 mg L- 1 of CVOl did not show behavioral changes up to 1 h after the start of the experiment ( Fig. 1D ). In the evaluation at 2, 3 and 6 h, 100% of the fish were in S2 stage. However, in the evaluation after 12 h until the last evaluation (48 h), 100% of the animals showed normal behavior. At a concentration of 80 mg L- 1, sedation (S2) was induced in 10 min. and lasted until 30 min. After 1 h from the beginning of the experiment, 62.5% of the fish were in the S3a stage and, after 2 h, the percentage of fish in this stage rose to 75%. In the 3-h assessment, 50% of the fish were in stage S3b, and the remaining ones were distributed between stages S3a and S2. After 6 h, the central depressant effect decreased, with 75% of animals in S2. In the evaluation 12 h after the start of the experiment, 100% of the fish were in S2 stage, and in the evaluations after 24 and 48 h, all returned to normal behavior. The 90 mg L- 1 concentration followed the same pattern as 80 mg L- 1 until 30 min., with all fish in S2. In the evaluation after 1 h, 100% of the animals were in S3a, and after 2 h, 62.5% of the animals continued in this stage and the remaining animals were in S2. After 3 h, 100% of the fish were in S3b, and in the next evaluation, 75% remained in S3b, with the other fish in S2. From this time on, the central depressant signs began to decrease and, at the last evaluation, all fish had returned to normal behavior. At 100 mg L- 1, after 10 and 20 min. 100% of the fish were in stage S2, in 30 min. 100% of the fish were in S3a and in the following evaluation, 100% were in S3b, remaining in this stage until 2 and 3 h after the beginning of the experiment. However, in the evaluation at 6 h, all animals regressed to stage S3a. From this time onwards, signs of central depression decreased until the 24-h assessment. However, at the end of the experiment (48 h), 12.5% of the animals were in S3a, 25% in S4 and the remaining fish were in S2.

Essential oil from leaves of Cordia verbenacea (CVOl).

At higher concentrations, CVOl showed a pattern of decreasing induction times for S2 stage, as the concentration increased. Through the curve ( Fig. 2D ) it is possible to infer that the concentration of 400 mg L- 1 (log = 2.6) induces this stage with an average time of 7.72 s. Stage S3a was not reached at concentrations of 50 mg L- 1 (log = 1.69) and 80 mg L- 1 (log = 1.9). However, the estimated curve for this stage generated a constant line, from the concentration of 100 mg L- 1 (log = 2.0) to 400 mg L- 1 (log = 2.6). Stage S3b was very similar to the previous one, also not being reached at concentrations of 50 mg L- 1 (log = 1.69) and 80 mg L- 1 (log = 1.9). At this stage, a constant pattern was also maintained, observing a smooth drop in time due to the increase in concentration. On the other hand, stage S4 was only reached from a concentration of 100 mg L- 1 (log = 2.0), with a reduction in time also being observed in this case because of the increase in concentrations. This pattern was not strong enough to change the pattern of the generated concentration-response curve. Thus, considering the induction of anesthesia stages, the curve indicates that the higher the concentration applied, the better and faster the response. In the case of the concentration-recovery response curve, it is clear that the higher the concentration applied, the longer it will take the fish to recover. In this way, at a concentration of 200 mg L- 1 (log = 2.3) the maximum acceptable time for stage S4 is reached.

Figures

FIGURE 1 | Stages of anesthesia observed over time in Rhamdia quelen (silver catfish) exposed to essential oil of inflorescences (A) and leaves (B) of Acmella oleracea, leaves (C) of Aloysia hatscbachii and leaves (D) of Cordia verbenacea. N - Normal behavior, S2 - sedation, S3a - partial loss of balance, S3b - total loss of balance, S4 - anesthesia, and S5 - bulbar collapse (n = 8).

FIGURE 2 | Graphic representation for the studied concentrations of the essential oils of Acmella oleracea inflorescences (A) and leaves (B), Aloysia hatschbachii leaves (C), and Cordia verbenacea leaves (D). The graphs were constructed from the equation described in item 2.7. The concentrations are represented in log form, being 20 mg L-1 (log = 1.3); 30 mg L-1 (log = 1.47); 50 mg L-1 (log = 1.69); 80 mg L-1 (log = 1.9); 100 mg L-1 (log = 2.00); 200 mg L-1 (log = 2.3); 300 mg L-1 (log = 2.47), and 400 mg L-1 (log = 2.6).