Oxidation is an essential process in the digestion of aerobic cells in the body. It involves the oxygen molecule, whose production through uncontrolled metabolic pathways leads to the formation of reactive oxygen species (ROS) such as superoxide ( O 2 − ⋅ ), hydroxyl ( H O ⋅ ), alkoxyl ( R O ⋅ ), and peroxyl ( R O O ⋅ ). These radicals are implicated in oxidative stress, which is characterized by an imbalance between the production of ROS (prooxidants) and the elimination of these species by the antioxidant defense mechanism [1].

Oxidative stress can damage molecules such as lipids, carbohydrates, proteins, and DNA. Free radicals are also implicated in the development of numerous diseases, including obesity, cancer, diabetes, inflammation, atherosclerosis, and neurodegenerative diseases [2][3].

Antioxidants are a family of substances that can neutralize free radicals and thus prevent the onset of diseases associated with oxidative stress. Among the best-known natural antioxidants are alpha-tocopherol (vitamin E), ascorbic acid (vitamin C), and phenolic compounds [4].

Insomnia is the most common sleep disorder encountered in sleep medicine. It is estimated that nearly 20% of the population suffers from chronic insomnia and 30% from occasional insomnia. Insomnia can be primary or secondary, and in both cases, transient (up to 3 months) or chronic (https://www.cenas.ch). Sedatives are a class of drugs used to treat anxiety and nervous tension. They soothe pain and facilitate sleep in cases of insomnia. They also help to relax agitated individuals. The person experiences a sense of calm; their breathing and reflexes slow down, and their muscles relax.

The genus Vitex is one of the largest genera in the Lamiaceae family, with approximately 250 species. It is widely distributed, but is found primarily in tropical zones with some in subtropical regions [5][6]. Among these species is Vitexmadiensis, which, due to its secondary metabolites. Indeed, this plant is widely used in traditional medicine to relieve or cure certain illnesses [7]-[9]. In Congo, people use it daily in the form of a tea locally called Tikoni, which means aches in the local language. Thus, the present study is undertaken to evaluate the antiradical and sedative effects of the aqueous extract of Tikoni, a preparation made from the leaves of V.madiensis, in laboratory mice.

TikoniTeaaqueousextractantiradicaleffect

Figure 1 shows the quantitative measurement of the antiradical effect of the aqueous extract of TIKONI tea. We observe that the percentage of inhibition increases with concentration. The percentages of free radical inhibition are 14.81%, 33.10%, 58.53%, and 74.81% for concentrations of 2.5, 5, 10, and 20 mg/ml, respectively.

Figure 1. Antiradical effect of Tikoni tea aqueous extract.

SedativeeffectofTikoniaqueousextract

-TranquilizingeffectofTikoniaqueousextract

Resultsofmotoractivitytest

Table 1 presents the results of the motor activity test in mice treated with aqueous extract of Tikoni tea at doses of 200 and 400 mg/kg. Aqueous extract of Tikoni tea significantly reduces motor activity at doses of 200 and 400 mg/kg. These results also show that the animals receiving the extract at a dose of 200 mg/kg crossed fewer squares compared to those receiving the extract at a dose of 400 mg/kg and the reference molecule, diazepam (10 mg/kg).

Table 1. Tikoni tea aqueous extract effect on the motor activity of the mouse.

(a): In mL/100 g. Values are means ± SEM, with n = 5; ***p < 0.001 significant difference compared to mice that received distilled water.

HypnoticeffectofTikoniteaaqueousextract

Table 2 presents the results of the barbiturate sleep test in mice under the effect of Tikoni tea aqueous extract, administered at doses of 200 and 400 mg/kg. These results show that Tikoni tea aqueous extract significantly decreases (***p < 0.001) the time to onset of barbiturate sleep in mice and significantly increases (***p < 0.001) the duration of barbiturate sleep in mice.

Table 2. Tikoni tea aqueous extract effect on barbiturate sleep in mice.

(a): In ml/100 g. (b): At 70 mg/kg. Values are means ± SEM, with n = 5; ***p < 0.001 significant difference compared to mice that received distilled water.

This work, which contributes to the valorization of Congolese medicinal and food plants, was initiated to evaluate the antiradical and sedative effect of the aqueous extract of Tikoni tea made from Vitexmadiensis leaves.

The DPPH test provides information on the reactivity of compounds with a stable free radical, DPPH, which exhibits a strong absorption band at 517 nm in the visible region. When the unpaired electron becomes paired in the presence of a free radical scavenger, absorption decreases and the DPPH solution is decolorized, changing from dark purple to light yellow. The degree of absorption reduction reflects the radical scavenging (antioxidant) capacity of compounds [15].

The results obtained show that the aqueous extract of Tikoni tea has free radical scavenging activity. Based on these results, a concentration of 8.54 mg/ml is required to inhibit 50% of free radicals. The inhibitory concentration (IC50) is inversely proportional to the antioxidant capacity of a compound. Indeed, if the IC50 is low, the plant has a high antioxidant potential [16][17].

The antioxidant activity of the aqueous extract of Tikoni tea can be attributed to the presence of identified phenolic compounds, flavonoids, and tannins found in Vitexmadiensis [12][18][19]. Flavonoids and tannins are phenolic compounds and plant phenolics constitute a major group of compounds that act as primary antioxidants or free radical scavengers [20].

The extract’s free radical scavenging properties may be an important contributing factor to the plant’s applications in the management and treatment of various diseases. Antioxidants prevent oxidative stress caused by free radicals that damage cells and vital biomolecules. They terminate the chain reactions triggered by free radicals by eliminating free radical intermediates and inhibiting other oxidation reactions.

Previous work on the leaves of other Vitex species has also shown the presence of phenolic compounds that could contribute to free radical scavenging activity [21][22]. Our results are consistent with those of Boungou-Tsona etal. (2023) [12], who also demonstrated, with the methanolic extract of Vitexmadiensis, a significant free radical scavenging activity correlated with a decrease in the production of reactive oxygen species (ROS), justified by the presence of ecdysteroids and flavonoids.

Similar activity has also been significantly demonstrated with the ethanolic extract and its hexane and ethyl acetate fractions on Vitexdonania, another species of the same family and genus as Vitexmadiensis, by Sarr etal. (2015) [22]. Using organic acid and ethanol extracts from the leaves of Vitexmadiensis Oliv., Ngbolua (2020) also demonstrated interesting antioxidant activity [8]. The unique aspect of our work is the demonstration of this activity in an aqueous extract within the real-world context of this plant’s use by farmers, without the use of an organic solvent.

To evaluate the sedative effect of aqueous Tikoni tea extract, two pharmacological tests were conducted: the tranquilizing effect by assessment of the extract’s effect on the motor activity of mice and the hypnotic effect by the potentiation of barbiturate-induced sleep.

At doses of 200 and 400 mg/kg, aqueous Tikoni tea extract significantly reduced motor activity compared to distilled water. Specifically, a marked reduction in motor activity was observed in animals receiving the extract at a dose of 200 mg/kg. It was also observed that mice that received the extract at a dose of 200 mg/kg had an average of 117.20 squares traversed compared to an average of squares traversed by mice that received distilled water (160.00) at 0.5 mL/100 g and diazepam (123.40) at 10 mg/kg. The effect of the extract on motor activity does not appear to be dose dependent.

At a dose of 400 mg/kg, the extract appears to have comparable effects to that observed with diazepam on reducing motor activity, with an average of 122.20 squares traversed by mice receiving the aqueous extract of Tikoni tea and an average of 123.40 squares traversed by those receiving diazepam at 10 mg/kg. Chemical screening performed by Ntandou et al. (2018) revealed the presence of flavonoids [1].

Thus, the effect of Tikoni tea on motor activity appears to be linked to the presence of secondary metabolites, particularly flavonoids, found in this plant. These results are similar to those obtained by Auniq and his colleagues, who evaluated the anxiolytic, sedative and antioxidant activity of Vitexpeduncularis and showed that flavonoids and tannins were at least partly responsible for the anxiolytic and sedative effects [13].

Tikoni tea significantly increased the onset and duration of barbiturate sleep, respectively, at doses of 200 and 400 mg/kg. Diazepam at 10 mg/kg was used as a reference. Diazepam decreased the onset of barbiturate sleep from 16.40 minutes (in negative controls) to 7 minutes. Diazepam increased the duration of barbiturate sleep from 12.76 minutes in negative controls to 19.76 minutes in positive controls. However, the aqueous extract of Tikoni tea appeared to be more effective than diazepam in potentiating barbiturate sleep at a dose of 400 mg/kg, with an increase of 23.4 minutes. The potentiation of sleep would be linked to the presence of flavonoids in this plant. Indeed, Marder (2012) demonstrated a selective affinity of natural flavonoids for the benzodiazepine binding site, with a broad spectrum of effects on the central nervous system [23]. However, unlike diazepam, the extract does not decrease sleep latency, but rather significantly increases it. It is possible that the extract acts as a mild sedative or an allosteric modulator of the GABAA receptor, slowing neuronal activity without inducing immediate hypnosis. This corresponds to a decrease in motor activity and an increase in sleep duration, but without the direct hypnotic effect of diazepam. Furthermore, the significant increase in sleep latency would indicate a stimulating effect [24]. This paradoxical profile could be explained by competition between different neurotransmitters stimulated or blocked by the extract. Indeed, an extract is a mixture of several chemical groups and molecules capable of acting simultaneously on different types of receptors and inducing different pharmacological effects [24].

Our results on the potentiation of barbiturate-induced sleep are similar to those obtained by Nkundineza etal. (2020), the potentiation of barbiturate-induced sleep is linked to the presence of phenolic compounds, specifically flavonoids [1][14].

The study found that the aqueous extract of Tikoni tea has antioxidant, sedative (tranquilizing and hypnotic), and significant effects, which could be attributed to its secondary metabolites, particularly phenolic compounds. However, this study used a crude extract, and the specific bioactive compounds responsible for these effects were not identified. Future work should focus on isolating and characterizing these active constituents to better understand the mechanisms underlying the observed activities.

The authors would like to thank Marien Ngouabi University for funding part of this work, Dr. Kami Emile for the botanical identification and authentication, and the traditional practitioners who contributed to the collection of plant material.