Handle JSON file using React

I'm using React for an application and I need to get some values from a JSON API.

API sample.

{
    "Meta Data": {
        "1. Information": "Intraday Prices and Volumes for Digital Currency",
        "2. Digital Currency Code": "BTC",
        "3. Digital Currency Name": "Bitcoin",
        "4. Market Code": "EUR",
        "5. Market Name": "Euro",
        "6. Interval": "5min",
        "7. Last Refreshed": "2018-08-15 22:00:00",
        "8. Time Zone": "UTC"
    },
    "Time Series (Digital Currency Intraday)": {
        "2018-08-15 22:00:00": {
            "1a. price (EUR)": "5648.06994794",
            "1b. price (USD)": "6409.19375195",
            "2. volume": "29868.07078908",
            "3. market cap (USD)": "191430252.68421999"
        },

Component:

import React, { Component } from 'react';

import Header from './Layout/Header/header';
import Tabela from './tabela';

class Page extends Component {
  constructor() {
    super();
    this.state = {
      ultimoValor: [],
      valor: []
    };
    this.getTime();
  }

  getTime() {
    let url = "https://www.alphavantage.co/query?function=DIGITAL_CURRENCY_INTRADAY&symbol=BTC&market=EUR&apikey=GU3DEGQIB86G05S2";
    fetch(url).then((response) => response.json()).then((responseJson) =>
    {
      this.setState({
        valor: responseJson
      });

    })
  }

  render() {
    return (
      <div>
        <Header />
        <Tabela valor={this.state.valor}/>
      </div>
    );
  }
}

But in the API, the given date ["Time Series (Digital Currency Intraday)"][ "2018-08-15 22:00:00"] is updated constantly and I tried the following in the getTime () function:

getTime() {
    let url = "https://www.alphavantage.co/query?function=DIGITAL_CURRENCY_INTRADAY&symbol=BTC&market=EUR&apikey=GU3DEGQIB86G05S2";
    fetch(url).then((response) => response.json()).then((responseJson) =>
    {
      this.setState({
        ultimoValor: responseJson["Meta Data"]["7. Last Refreshed"],
        valor: responseJson["Time Series (Digital Currency Intraday)"][{this.state.ultimoValor}]["1a. price (EUR)"]
      });

    })
  }

I believe the error is in the assignment of valor , because when I pass [{this.state.ultimoValor}] it does not take the state value.