Effect of caffeine, caffeic acid and their various combinations on enzymes of cholinergic, monoaminergic and purinergic systems critical to neurodegeneration in rat brain-In vitro

Caffeine and caffeic acid are two bioactive compounds that are present in plant foods and are major constituent of coffee, cocoa, tea, cola drinks and chocolate. Although not structurally related, caffeine and caffeic acid has been reported to elicit neuroprotective properties. However, their different proportional distribution in food sources and possible effect of such interactions are not often taken into consideration. Therefore, in this study, we investigated the effect of caffeine, caffeic acid and their various combinations on activities of some enzymes [acetylcholinesterase (AChE), monoamine oxidase (MAO) ecto-nucleoside triphosphate diphosphohydrolase (E-NTPase), ecto-5¹-nucleotidase (E-NTDase) and Na⁺/K⁺ ATPase relevant to neurodegeneration in vitro in rat brain. The stock concentration of caffeine and caffiec acid and their various proportional combinations were prepared and their interactions with the activities of these enzymes were assessed (in vitro) in different brain structures. The Fe²⁺ and Cu²⁺ chelating abilities of the samples were also investigated. The results revealed that caffeine, caffeic acid and their various combinations exhibited inhibitory effect on activities of AChE, MAO, E-NTPase and E-NTDase, but stimulatory effect on Na⁺/K⁺ ATPase activity. The combinations also exhibited Fe²⁺ and Cu²⁺ chelating abilities. Considering the various combinations, a higher caffeine to caffeic acid ratio produced significantly highest enzyme modulatory effects; these were significantly lower to the effect of caffeine alone but significantly higher than the effect of caffeic acid alone. These findings may provide new insight into the effect of proportional combination of these bioactive compounds as obtained in many foods especially with respect to their neuroprotective effects.

Phenolic compounds from sandpaper (ficus exasperata) leaf inhibits angiotensin 1 converting enzyme in high cholesterol diet fed rats

ETHNOPHARMACOLOGICAL RELEVANCE

Sandpaper [Ficus exasperata Vahl (Moraceae)] leaf has been reportedly used in folklore for the management/treatment of cardiovascular diseases with little/or no scientific basis for their action. This study sought to investigate the effect of dietary supplementation of sandpaper leaf on angiotensin-I converting enzyme (ACE) activity in hypercholesterolemia as well as the effect of their phenolic extract on this enzyme in vitro.

MATERIALS AND METHODS

The phenolic extract was prepared, then, the inhibitory effect of the leaf extract on ACE was determined in vitro. Thereafter, the effect of dietary supplementation of sandpaper leaf on angiotensin-I converting enzyme (ACE) activity in high cholesterol diet fed rats for 14 days was evaluated as well as some biochemical parameters.

RESULTS

The result revealed that under in vitro condition, the phenolic extract inhibited ACE (IC50=14.7µg/mL) in a dose-dependent manner (0-10µg/mL). Feeding high cholesterol diets to rats caused a significant (P<0.05) increase in the ACE activity. However, there was a significant (P<0.05) decrease in the ACE activity as a result of supplementation with the sand paper leaves. Furthermore, there was a significant (P<0.05) increase in the plasma lipid profile with a concomitant increase in malondialdehyde (MDA) content in rat liver and heart tissues. However, supplementing the diet with sandpaper leaf (either 10% or 20%) caused a significant (P<0.05) decrease in the plasma total cholesterol (TC), triglyceride (TG), very low density lipoprotein-cholesterol (VLDL-C), and low-density lipoprotein-cholesterol levels (LDL-C), and in MDA content in the tissues. Conversely, supplementation caused a significant (P<0.05) increase in plasma high-density lipoprotein-cholesterol level when compared with the control diet. Reversed phase HPLC analysis of the extract revealed Quercitrin (43.7mg/g), chlorogenic acid (42.8mg/g) and caffeic acid (33.9mg/g) as the major phenolics in the leaf.

CONCLUSION

The inhibition of ACE activity and prevention of hypercholesterolemia by sandpaper leaf could be part of the possible mechanism underlying its anti-hypertensive property which could lay credence to its use in folk medicine. However, these activities may be directly/indirectly attributed to the polyphenolics present.

Inhibition of α-amylase and α-glucosidase activities by ethanolic extract of Telfairia occidentalis (fluted pumpkin) leaf

OBJECTIVE

To investigate the inhibitory effect of Telfairia occidentalis Hook f. (Curcubitaceae) (T. occidentalis) leaf on key enzyme linked to type-2 diabetes (α - amylase and α - glucosidase) as well as assess the effect of blanching (a commonly practiced food processing technique) of the vegetable on these key enzymes.

METHODS

Fresh leaves of T. occidentalis were blanched in hot water for 10 minutes, and the extracts of both the fresh and blanched vegetables were prepared and used for subsequent analysis. The inhibitory effect of the extract on α - amylase and α - glucosidase activities as well as some antioxidant parameter was determined in vitro.

RESULTS

The result revealed that unprocessed T. occidentalis leaf reduce Fe(3+) to Fe(2+) and also inhibited α - amylase and α - glucosidase activities in a dose dependent manner. However, blanching of the leafy vegetables caused a significant (P<0.05) increase in the antioxidant properties but decrease their ability to inhibit α - amylase and α - glucosidase activities.

CONCLUSIONS

This antioxidant properties and enzyme inhibition could be part of the mechanism by which they are used in the treatment/prevention of type-2 diabetes. However, the blanched vegetable reduces their ability to inhibit both α - amylase and α - glucosidase activity in vitro.