Kalanchoe crenata Andrews (Haw.) Improves Losartan's Antihypertensive Activity

Abstract

Background: Cardiovascular diseases constitute one of the leading causes of morbidity and mortality worldwide. Herbal medicines represent viable alternatives to the synthetic drugs currently employed in the control of hypertension. This study aimed to isolate and identify the chemical markers of Kalanchoe crenata and to investigate the antihypertensive and anti-matrix metalloproteinase (MMP2) activities of an aqueous extract of the leaves.

Methods: The main constituents of the aqueous extract of K. crenata were separated by ultra-performance liquid chromatography-mass spectrometry, and their presence was identified by NMR spectroscopy. Renovascular hypertension was induced in male Wistar rats using the two-kidney one-clip method (HTN groups), while control animals (Sham groups) were submitted to Sham surgery. Six groups of 10 animals each were treated daily for eight weeks as follows: Sham 1 (carrier), Sham 2 (K. crenata extract), HTN.1 (carrier), HTN.2 (K. crenata extract), HTN 3 (losartan), and HTN 4 (K. crenata extract with losartan).

Results: The main compounds of the extract were patuletin 3-O-(4″-O-acetyl-α-L-rhamnopyranosyl)-7-O-(3‴-O-acetyl-α-L-rhamnopyranoside) (1), patuletin 3-O-α-L-rhamnopyranosyl-7-O-L-rhamnopyranoside (2), and trans-caffeoyl-malic acid (3), with compounds 1 and 2 being chemical markers of the species. Significant reductions (p < 0.05) in systolic blood pressure and MMP2 (72kDa isoform) activity were observed in the HTN 4 group.

Conclusions: The association of K. crenata extract and losartan presented in vivo effects against hypertension.

Keywords: hypertension; medicinal plant; murine model; patuletins; systolic blood pressure.

Figure 1

Compounds isolated from the aqueous extract of Kalanchoe crenata leaves are as follows: 1—patuletin 3-O-(4″-O-acetyl-α-L-rhamnopyranosyl)-7-O-(3‴-O-acetyl-α-L-rhamnopyranoside); 2—patuletin 3-O-α-L-rhamnopyranosyl-7-O-L-rhamnopyranoside; and 3—trans-caffeoyl-malic acid or phaselic acid.

Figure 2

Cardiac hypertrophy indices of normotensive and hypertensive rats determined as the ratio of heart weight (g) to tibia length (cm). Normotensive rats were submitted to Sham surgery and treated with the carrier alone (Sham 1) or with 300 mg/kg Kalanchoe crenata extract (Sham 2). Hypertensive rats were submitted to the two-kidney one-clip (2K1C) procedure and treated with the carrier alone (HTN 1), with 300 mg/kg K. crenata extract (HTN 2), with 10 mg losartan (HTN 3), or with 300 mg/kg K. crenata extract and 10 mg losartan (HTN 4). Significant differences in relation to HTN1 are indicated by asterisks as follows: p < 0.05 (*) and p < 0.01 (**).

Figure 3

Thickness of the middle layer of the aortic wall of normotensive and hypertensive rats as shown by the following: (A) measurements taken from images obtained using an optical microscope and processed with the help of ImageJ 1.46r software; and (B) sections stained with hematoxylin and eosin. Normotensive rats were submitted to Sham surgery and treated with the carrier alone (Sham 1) or with 300 mg/kg Kalanchoe crenata extract (Sham 2). Hypertensive rats were submitted to the two-kidney one-clip (2K1C) procedure and treated with the carrier alone (HTN 1), with 300 mg/kg K. crenata extract (HTN 2), with 10 mg losartan (HTN 3), or with 300 mg/kg K. crenata extract and 10 mg losartan (HTN 4). Significant differences in relation to HTN1 are indicated by asterisks as follows: p < 0.05 (*) and p < 0.01 (**).

Figure 4

Systolic blood pressure (SBP) of normotensive and hypertensive rats. Normotensive rats were submitted to Sham surgery and treated with the carrier alone (Sham 1) or with 300 mg/kg Kalanchoe crenata extract (Sham 2). Hypertensive rats were submitted to the two-kidney one-clip (2K1C) procedure and treated with the carrier alone (HTN 1), with 300 mg/kg K. crenata extract (HTN 2), with 10 mg losartan (HTN 3), or with 300 mg/kg K. crenata extract and 10 mg losartan (HTN 4). Significant differences are indicated by * (p < 0.05) for Sham 1/Sham 2/HTN 4 versus HTN 1/HTN 2/HTN 3, and by # (p < 0.05) for HTN 1 versus HTN 2/HTN 3.

Figure 5

(A) The gel shows the zymography of the 75 kDa, 72 kDa, and 64 kDa isoforms for each experimental group together with internal standard. (B) Activities of MMP2 isoforms in the aortic tissue of normotensive and hypertensive rats. Normotensive rats were submitted to Sham surgery and treated with the carrier alone (Sham 1) or with 300 mg/kg Kalanchoe crenata extract (Sham 2). Hypertensive rats were submitted to the two-kidney one-clip (2K1C) procedure and treated with the carrier alone (HTN 1), with 300 mg/kg K. crenata extract (HTN 2), with 10 mg losartan (HTN 3), or with 300 mg/kg K. crenata extract and 10 mg losartan (HTN 4). Significant differences in relation to HTN1 are indicated by asterisks as follows: p < 0.05 (*) and p < 0.01 (**).